Merge pull request 'Initial implementation of readable streams' (#2324) from dbsoft/UXP:readablestreams into master

Reviewed-on: https://repo.palemoon.org/MoonchildProductions/UXP/pulls/2324

59 files changed, 3206 insertions, 1062 deletions

diff --git a/dom/base/FormData.cpp b/dom/base/FormData.cpp
index de4d71a676..d47a970fc8 100644
--- a/dom/base/FormData.cpp
+++ b/dom/base/FormData.cpp
@@ -398,7 +398,7 @@ FormData::Constructor(const GlobalObject& aGlobal,
 
 NS_IMETHODIMP
 FormData::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
-                      nsACString& aContentType, nsACString& aCharset)
+                      nsACString& aContentTypeWithCharset, nsACString& aCharset)
 {
   FSMultipartFormData fs(NS_LITERAL_CSTRING("UTF-8"), nullptr);
 
@@ -419,7 +419,7 @@ FormData::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
     }
   }
 
-  fs.GetContentType(aContentType);
+  fs.GetContentType(aContentTypeWithCharset);
   aCharset.Truncate();
   *aContentLength = 0;
   NS_ADDREF(*aBody = fs.GetSubmissionBody(aContentLength));
diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
index 05268a5156..0bf9ccbf45 100644
--- a/dom/base/Navigator.cpp
+++ b/dom/base/Navigator.cpp
@@ -11,7 +11,9 @@
 #include "nsPluginArray.h"
 #include "nsMimeTypeArray.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/BodyExtractor.h"
 #include "mozilla/dom/DesktopNotification.h"
+#include "mozilla/dom/FetchBinding.h"
 #include "mozilla/dom/File.h"
 #include "nsGeolocation.h"
 #include "nsIClassOfService.h"
@@ -38,6 +40,7 @@
 #include "mozilla/dom/ServiceWorkerContainer.h"
 #include "mozilla/dom/StorageManager.h"
 #include "mozilla/dom/TCPSocket.h"
+#include "mozilla/dom/URLSearchParams.h"
 #include "mozilla/dom/workers/RuntimeService.h"
 #include "mozilla/Hal.h"
 #include "nsISiteSpecificUserAgent.h"
@@ -845,9 +848,53 @@ BeaconStreamListener::OnDataAvailable(nsIRequest *aRequest,
 
 bool
 Navigator::SendBeacon(const nsAString& aUrl,
-                      const Nullable<ArrayBufferViewOrBlobOrStringOrFormData>& aData,
+                      const Nullable<fetch::BodyInit>& aData,
                       ErrorResult& aRv)
 {
+  if (aData.IsNull()) {
+    return SendBeaconInternal(aUrl, nullptr, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsArrayBuffer()) {
+    BodyExtractor<const ArrayBuffer> body(&aData.Value().GetAsArrayBuffer());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsArrayBufferView()) {
+    BodyExtractor<const ArrayBufferView> body(&aData.Value().GetAsArrayBufferView());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsBlob()) {
+    BodyExtractor<nsIXHRSendable> body(&aData.Value().GetAsBlob());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsFormData()) {
+    BodyExtractor<nsIXHRSendable> body(&aData.Value().GetAsFormData());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsUSVString()) {
+    BodyExtractor<const nsAString> body(&aData.Value().GetAsUSVString());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  if (aData.Value().IsURLSearchParams()) {
+    BodyExtractor<nsIXHRSendable> body(&aData.Value().GetAsURLSearchParams());
+    return SendBeaconInternal(aUrl, &body, eBeaconTypeOther, aRv);
+  }
+
+  MOZ_CRASH("Invalid data type.");
+  return false;
+}
+
+bool
+Navigator::SendBeaconInternal(const nsAString& aUrl,
+                              BodyExtractorBase* aBody,
+                              BeaconType aType,
+                              ErrorResult& aRv)
+{
   if (!mWindow) {
     aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
     return false;
@@ -887,9 +934,9 @@ Navigator::SendBeacon(const nsAString& aUrl,
   nsLoadFlags loadFlags = nsIRequest::LOAD_NORMAL;
 
   // No need to use CORS for sendBeacon unless it's a BLOB
-  nsSecurityFlags securityFlags = (!aData.IsNull() && aData.Value().IsBlob())
-   ? nsILoadInfo::SEC_REQUIRE_CORS_DATA_INHERITS
-   : nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_INHERITS;
+  nsSecurityFlags securityFlags = aType == eBeaconTypeBlob
+    ? nsILoadInfo::SEC_REQUIRE_CORS_DATA_INHERITS
+    : nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_INHERITS;
   securityFlags |= nsILoadInfo::SEC_COOKIES_INCLUDE;
 
   nsCOMPtr<nsIChannel> channel;
@@ -915,76 +962,30 @@ Navigator::SendBeacon(const nsAString& aUrl,
   }
   httpChannel->SetReferrer(documentURI);
 
-  nsCString mimeType;
-  if (!aData.IsNull()) {
-    nsCOMPtr<nsIInputStream> in;
-
-    if (aData.Value().IsString()) {
-      nsCString stringData = NS_ConvertUTF16toUTF8(aData.Value().GetAsString());
-      nsCOMPtr<nsIStringInputStream> strStream = do_CreateInstance(NS_STRINGINPUTSTREAM_CONTRACTID, &rv);
-      if (NS_FAILED(rv)) {
-        aRv.Throw(NS_ERROR_FAILURE);
-        return false;
-      }
-      rv = strStream->SetData(stringData.BeginReading(), stringData.Length());
-      if (NS_FAILED(rv)) {
-        aRv.Throw(NS_ERROR_FAILURE);
-        return false;
-      }
-      mimeType.AssignLiteral("text/plain;charset=UTF-8");
-      in = strStream;
-
-    } else if (aData.Value().IsArrayBufferView()) {
-
-      nsCOMPtr<nsIStringInputStream> strStream = do_CreateInstance(NS_STRINGINPUTSTREAM_CONTRACTID, &rv);
-      if (NS_FAILED(rv)) {
-        aRv.Throw(NS_ERROR_FAILURE);
-        return false;
-      }
-
-      const ArrayBufferView& view = aData.Value().GetAsArrayBufferView();
-      view.ComputeLengthAndData();
-      rv = strStream->SetData(reinterpret_cast<char*>(view.Data()),
-                              view.Length());
-
-      if (NS_FAILED(rv)) {
-        aRv.Throw(NS_ERROR_FAILURE);
-        return false;
-      }
-      mimeType.AssignLiteral("application/octet-stream");
-      in = strStream;
-
-    } else if (aData.Value().IsBlob()) {
-      Blob& blob = aData.Value().GetAsBlob();
-      blob.GetInternalStream(getter_AddRefs(in), aRv);
-      if (NS_WARN_IF(aRv.Failed())) {
-        return false;
-      }
+  nsCOMPtr<nsIInputStream> in;
+  nsAutoCString contentTypeWithCharset;
+  nsAutoCString charset;
+  uint64_t length = 0;
 
-      nsAutoString type;
-      blob.GetType(type);
-      mimeType = NS_ConvertUTF16toUTF8(type);
-
-    } else if (aData.Value().IsFormData()) {
-      FormData& form = aData.Value().GetAsFormData();
-      uint64_t len;
-      nsAutoCString charset;
-      form.GetSendInfo(getter_AddRefs(in),
-                       &len,
-                       mimeType,
-                       charset);
-    } else {
-      MOZ_ASSERT(false, "switch statements not in sync");
-      aRv.Throw(NS_ERROR_FAILURE);
+  if (aBody) {
+    aRv = aBody->GetAsStream(getter_AddRefs(in), &length,
+                             contentTypeWithCharset, charset);
+    if (NS_WARN_IF(aRv.Failed())) {
       return false;
     }
 
+    if (aType == eBeaconTypeArrayBuffer) {
+      MOZ_ASSERT(contentTypeWithCharset.IsEmpty());
+      MOZ_ASSERT(charset.IsEmpty());
+      contentTypeWithCharset.Assign("application/octet-stream");
+    }
+
     nsCOMPtr<nsIUploadChannel2> uploadChannel = do_QueryInterface(channel);
     if (!uploadChannel) {
       aRv.Throw(NS_ERROR_FAILURE);
       return false;
     }
-    uploadChannel->ExplicitSetUploadStream(in, mimeType, -1,
+    uploadChannel->ExplicitSetUploadStream(in, contentTypeWithCharset, length,
                                            NS_LITERAL_CSTRING("POST"),
                                            false);
   } else {
diff --git a/dom/base/Navigator.h b/dom/base/Navigator.h
index 2915b50692..175940e82d 100644
--- a/dom/base/Navigator.h
+++ b/dom/base/Navigator.h
@@ -7,6 +7,7 @@
 #define mozilla_dom_Navigator_h
 
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/Fetch.h"
 #include "mozilla/dom/Nullable.h"
 #include "mozilla/ErrorResult.h"
 #include "nsIDOMNavigator.h"
@@ -30,12 +31,13 @@ class nsIURI;
 
 namespace mozilla {
 namespace dom {
+class BodyExtractorBase;
 class Geolocation;
 class systemMessageCallback;
 class MediaDevices;
 struct MediaStreamConstraints;
 class WakeLock;
-class ArrayBufferViewOrBlobOrStringOrFormData;
+class ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams;
 class ServiceWorkerContainer;
 class DOMRequest;
 } // namespace dom
@@ -196,7 +198,7 @@ public:
 #endif // MOZ_AUDIO_CHANNEL_MANAGER
 
   bool SendBeacon(const nsAString& aUrl,
-                  const Nullable<ArrayBufferViewOrBlobOrStringOrFormData>& aData,
+                  const Nullable<fetch::BodyInit>& aData,
                   ErrorResult& aRv);
 
   void MozGetUserMedia(const MediaStreamConstraints& aConstraints,
@@ -253,6 +255,19 @@ private:
   bool CheckPermission(const char* type);
   static bool CheckPermission(nsPIDOMWindowInner* aWindow, const char* aType);
 
+  // This enum helps SendBeaconInternal to apply different behaviors to body
+  // types.
+  enum BeaconType {
+    eBeaconTypeBlob,
+    eBeaconTypeArrayBuffer,
+    eBeaconTypeOther
+  };
+
+  bool SendBeaconInternal(const nsAString& aUrl,
+                          BodyExtractorBase* aBody,
+                          BeaconType aType,
+                          ErrorResult& aRv);
+
   RefPtr<nsMimeTypeArray> mMimeTypes;
   RefPtr<nsPluginArray> mPlugins;
   RefPtr<Permissions> mPermissions;
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 86e52984af..4c00f358f2 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -39,6 +39,8 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/CustomElementRegistry.h"
 #include "mozilla/dom/DocumentFragment.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/DOMExceptionBinding.h"
 #include "mozilla/dom/DOMTypes.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/FileSystemSecurity.h"
@@ -8735,6 +8737,25 @@ nsContentUtils::PushEnabled(JSContext* aCx, JSObject* aObj)
 
 // static
 bool
+nsContentUtils::StreamsEnabled(JSContext* aCx, JSObject* aObj)
+{
+  if (NS_IsMainThread()) {
+    return Preferences::GetBool("dom.streams.enabled", false);
+  }
+
+  using namespace workers;
+
+  // Otherwise, check the pref via the WorkerPrivate
+  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+  if (!workerPrivate) {
+    return false;
+  }
+
+  return workerPrivate->StreamsEnabled();
+}
+
+// static
+bool
 nsContentUtils::IsNonSubresourceRequest(nsIChannel* aChannel)
 {
   nsLoadFlags loadFlags = 0;
@@ -10060,3 +10081,72 @@ void nsContentUtils::StructuredClone(JSContext* aCx,
   nsTArray<RefPtr<MessagePort>> ports = holder.TakeTransferredPorts();
   Unused << ports;
 }
+
+/* static */ void
+nsContentUtils::ExtractErrorValues(JSContext* aCx,
+                                   JS::Handle<JS::Value> aValue,
+                                   nsACString& aSourceSpecOut,
+                                   uint32_t* aLineOut,
+                                   uint32_t* aColumnOut,
+                                   nsString& aMessageOut)
+{
+  MOZ_ASSERT(aLineOut);
+  MOZ_ASSERT(aColumnOut);
+
+  if (aValue.isObject()) {
+    JS::Rooted<JSObject*> obj(aCx, &aValue.toObject());
+    RefPtr<dom::DOMException> domException;
+
+    // Try to process as an Error object.  Use the file/line/column values
+    // from the Error as they will be more specific to the root cause of
+    // the problem.
+    JSErrorReport* err = obj ? JS_ErrorFromException(aCx, obj) : nullptr;
+    if (err) {
+      // Use xpc to extract the error message only.  We don't actually send
+      // this report anywhere.
+      RefPtr<xpc::ErrorReport> report = new xpc::ErrorReport();
+      report->Init(err,
+                   "<unknown>", // toString result
+                   false,       // chrome
+                   0);          // window ID
+
+      if (!report->mFileName.IsEmpty()) {
+        CopyUTF16toUTF8(report->mFileName, aSourceSpecOut);
+        *aLineOut = report->mLineNumber;
+        *aColumnOut = report->mColumn;
+      }
+      aMessageOut.Assign(report->mErrorMsg);
+    }
+
+    // Next, try to unwrap the rejection value as a DOMException.
+    else if(NS_SUCCEEDED(UNWRAP_OBJECT(DOMException, obj, domException))) {
+
+      nsAutoString filename;
+      domException->GetFilename(aCx, filename);
+      if (!filename.IsEmpty()) {
+        CopyUTF16toUTF8(filename, aSourceSpecOut);
+        *aLineOut = domException->LineNumber(aCx);
+        *aColumnOut = domException->ColumnNumber();
+      }
+
+      domException->GetName(aMessageOut);
+      aMessageOut.AppendLiteral(": ");
+
+      nsAutoString message;
+      domException->GetMessageMoz(message);
+      aMessageOut.Append(message);
+    }
+  }
+
+  // If we could not unwrap a specific error type, then perform default safe
+  // string conversions on primitives.  Objects will result in "[Object]"
+  // unfortunately.
+  if (aMessageOut.IsEmpty()) {
+    nsAutoJSString jsString;
+    if (jsString.init(aCx, aValue)) {
+      aMessageOut = jsString;
+    } else {
+      JS_ClearPendingException(aCx);
+    }
+  }
+}
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index 58f9f56546..6e9f23054a 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -1010,6 +1010,10 @@ public:
 
   static bool PrefetchEnabled(nsIDocShell* aDocShell);
 
+  static void ExtractErrorValues(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                                 nsACString& aSourceSpecOut, uint32_t *aLineOut,
+                                 uint32_t *aColumnOut, nsString& aMessageOut);
+
   static nsresult CalculateBufferSizeForImage(const uint32_t& aStride,
                                               const mozilla::gfx::IntSize& aImageSize,
                                               const mozilla::gfx::SurfaceFormat& aFormat,
@@ -2679,6 +2683,8 @@ public:
   static mozilla::net::ReferrerPolicy GetReferrerPolicyFromHeader(const nsAString& aHeader);
 
   static bool PushEnabled(JSContext* aCx, JSObject* aObj);
+  
+  static bool StreamsEnabled(JSContext* aCx, JSObject* aObj);
 
   static bool IsNonSubresourceRequest(nsIChannel* aChannel);
 
diff --git a/dom/bindings/Bindings.conf b/dom/bindings/Bindings.conf
index a12a294766..17bbed79d5 100644
--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -103,11 +103,13 @@ DOMInterfaces = {
 },
 
 'Cache': {
-    'implicitJSContext': [ 'add', 'addAll' ],
+    'implicitJSContext': [ 'add', 'addAll', 'match', 'matchAll', 'put',
+                           'delete', 'keys' ],
     'nativeType': 'mozilla::dom::cache::Cache',
 },
 
 'CacheStorage': {
+    'implicitJSContext': [ 'match' ],
     'nativeType': 'mozilla::dom::cache::CacheStorage',
 },
 
@@ -705,6 +707,7 @@ DOMInterfaces = {
         'headers': 'headers_',
         'referrerPolicy': 'referrerPolicy_'
     },
+    'implicitJSContext': [ 'arrayBuffer', 'blob', 'formData', 'json', 'text' ],
 },
 
 'ResizeObservation': {
@@ -729,6 +732,8 @@ DOMInterfaces = {
 
 'Response': {
     'binaryNames': { 'headers': 'headers_' },
+    'implicitJSContext': [ 'arrayBuffer', 'blob', 'formData', 'json', 'text',
+                           'clone', 'cloneUnfiltered' ],
 },
 
 'RGBColor': {
diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index a70253fc3a..b7caaad7bb 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -1156,7 +1156,10 @@ class CGHeaders(CGWrapper):
                         # just include their header if we need to have functions
                         # taking references to them declared in that header.
                         headerSet = declareIncludes
-                    headerSet.add("mozilla/dom/TypedArray.h")
+                    if unrolled.isReadableStream():
+                        headerSet.add("mozilla/dom/ReadableStream.h")
+                    else:
+                        headerSet.add("mozilla/dom/TypedArray.h")
                 else:
                     try:
                         typeDesc = config.getDescriptor(unrolled.inner.identifier.name)
@@ -1371,7 +1374,10 @@ def UnionTypes(unionTypes, config):
                 elif f.isInterface():
                     if f.isSpiderMonkeyInterface():
                         headers.add("jsfriendapi.h")
-                        headers.add("mozilla/dom/TypedArray.h")
+                        if f.isReadableStream():
+                            headers.add("mozilla/dom/ReadableStream.h")
+                        else:
+                            headers.add("mozilla/dom/TypedArray.h")
                     else:
                         try:
                             typeDesc = config.getDescriptor(f.inner.identifier.name)
@@ -1457,7 +1463,10 @@ def UnionConversions(unionTypes, config):
                 elif f.isInterface():
                     if f.isSpiderMonkeyInterface():
                         headers.add("jsfriendapi.h")
-                        headers.add("mozilla/dom/TypedArray.h")
+                        if f.isReadableStream():
+                            headers.add("mozilla/dom/ReadableStream.h")
+                        else:
+                            headers.add("mozilla/dom/TypedArray.h")
                     elif f.inner.isExternal():
                         try:
                             typeDesc = config.getDescriptor(f.inner.identifier.name)
@@ -5582,8 +5591,8 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
     if type.isSpiderMonkeyInterface():
         assert not isEnforceRange and not isClamp
         name = type.unroll().name  # unroll() because it may be nullable
-        arrayType = CGGeneric(name)
-        declType = arrayType
+        interfaceType = CGGeneric(name)
+        declType = interfaceType
         if type.nullable():
             declType = CGTemplatedType("Nullable", declType)
             objRef = "${declName}.SetValue()"
@@ -5607,22 +5616,23 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
             # This is a bit annoying.  In a union we don't want to have a
             # holder, since unions don't support that.  But if we're optional we
             # want to have a holder, so that the callee doesn't see
-            # Optional<RootedTypedArray<ArrayType> >.  So do a holder if we're
-            # optional and use a RootedTypedArray otherwise.
+            # Optional<RootedSpiderMonkeyInterface<InterfaceType>>.  So do a
+            # holder if we're optional and use a RootedSpiderMonkeyInterface
+            # otherwise.
             if isOptional:
-                holderType = CGTemplatedType("TypedArrayRooter", arrayType)
-                # If our typed array is nullable, this will set the Nullable to
-                # be not-null, but that's ok because we make an explicit
-                # SetNull() call on it as needed if our JS value is actually
-                # null.  XXXbz Because "Maybe" takes const refs for constructor
-                # arguments, we can't pass a reference here; have to pass a
-                # pointer.
+                holderType = CGTemplatedType("SpiderMonkeyInterfaceRooter", interfaceType)
+                # If our SpiderMonkey interface is nullable, this will set the
+                # Nullable to be not-null, but that's ok because we make an
+                # explicit SetNull() call on it as needed if our JS value is
+                # actually null.  XXXbz Because "Maybe" takes const refs for
+                # constructor arguments, we can't pass a reference here; have
+                # to pass a pointer.
                 holderArgs = "cx, &%s" % objRef
                 declArgs = None
             else:
                 holderType = None
                 holderArgs = None
-                declType = CGTemplatedType("RootedTypedArray", declType)
+                declType = CGTemplatedType("RootedSpiderMonkeyInterface", declType)
                 declArgs = "cx"
         else:
             holderType = None
@@ -6371,7 +6381,7 @@ def getMaybeWrapValueFuncForType(type):
         if type.nullable():
             return "MaybeWrapObjectOrNullValue"
         return "MaybeWrapObjectValue"
-    # Spidermonkey interfaces are never DOM objects.  Neither are sequences or
+    # SpiderMonkey interfaces are never DOM objects.  Neither are sequences or
     # dictionaries, since those are always plain JS objects.
     if type.isSpiderMonkeyInterface() or type.isDictionary() or type.isSequence():
         if type.nullable():
@@ -6391,7 +6401,8 @@ recordWrapLevel = 0
 
 
 def getWrapTemplateForType(type, descriptorProvider, result, successCode,
-                           returnsNewObject, exceptionCode, typedArraysAreStructs,
+                           returnsNewObject, exceptionCode,
+                           spiderMonkeyInterfacesAreStructs,
                            isConstructorRetval=False):
     """
     Reflect a C++ value stored in "result", of IDL type "type" into JS.  The
@@ -6401,8 +6412,9 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
     doing a 'break' if the entire conversion template is inside a block that
     the 'break' will exit).
 
-    If typedArraysAreStructs is true, then if the type is a typed array,
-    "result" is one of the dom::TypedArray subclasses, not a JSObject*.
+    If spiderMonkeyInterfacesAreStructs is true, then if the type is a
+    SpiderMonkey interface, "result" is one of the
+    dom::SpiderMonkeyInterfaceObjectStorage subclasses, not a JSObject*.
 
     The resulting string should be used with string.Template.  It
     needs the following keys when substituting:
@@ -6497,7 +6509,7 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
         recTemplate, recInfall = getWrapTemplateForType(type.inner, descriptorProvider,
                                                         "%s.Value()" % result, successCode,
                                                         returnsNewObject, exceptionCode,
-                                                        typedArraysAreStructs)
+                                                        spiderMonkeyInterfacesAreStructs)
         code = fill(
             """
 
@@ -6529,7 +6541,7 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
                 'returnsNewObject': returnsNewObject,
                 'exceptionCode': exceptionCode,
                 'obj': "returnArray",
-                'typedArraysAreStructs': typedArraysAreStructs
+                'spiderMonkeyInterfacesAreStructs': spiderMonkeyInterfacesAreStructs
             })
         sequenceWrapLevel -= 1
         code = fill(
@@ -6583,7 +6595,7 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
                 'returnsNewObject': returnsNewObject,
                 'exceptionCode': exceptionCode,
                 'obj': "returnObj",
-                'typedArraysAreStructs': typedArraysAreStructs
+                'spiderMonkeyInterfacesAreStructs': spiderMonkeyInterfacesAreStructs
             })
         recordWrapLevel -= 1
         if type.keyType.isByteString():
@@ -6749,7 +6761,7 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
         return (head + _setValue(result, wrapAsType=type), False)
 
     if (type.isObject() or (type.isSpiderMonkeyInterface() and
-                            not typedArraysAreStructs)):
+                            not spiderMonkeyInterfacesAreStructs)):
         # See comments in GetOrCreateDOMReflector explaining why we need
         # to wrap here.
         if type.nullable():
@@ -6768,21 +6780,21 @@ def getWrapTemplateForType(type, descriptorProvider, result, successCode,
 
     if not (type.isUnion() or type.isPrimitive() or type.isDictionary() or
             type.isDate() or
-            (type.isSpiderMonkeyInterface() and typedArraysAreStructs)):
+            (type.isSpiderMonkeyInterface() and spiderMonkeyInterfacesAreStructs)):
         raise TypeError("Need to learn to wrap %s" % type)
 
     if type.nullable():
         recTemplate, recInfal = getWrapTemplateForType(type.inner, descriptorProvider,
                                                        "%s.Value()" % result, successCode,
                                                        returnsNewObject, exceptionCode,
-                                                       typedArraysAreStructs)
+                                                       spiderMonkeyInterfacesAreStructs)
         return ("if (%s.IsNull()) {\n" % result +
                 indent(setNull()) +
                 "}\n" +
                 recTemplate, recInfal)
 
     if type.isSpiderMonkeyInterface():
-        assert typedArraysAreStructs
+        assert spiderMonkeyInterfacesAreStructs
         # See comments in GetOrCreateDOMReflector explaining why we need
         # to wrap here.
         # NB: setObject(..., some-object-type) calls JS_WrapValue(), so is fallible
@@ -6864,7 +6876,7 @@ def wrapForType(type, descriptorProvider, templateValues):
         templateValues.get('successCode', None),
         templateValues.get('returnsNewObject', False),
         templateValues.get('exceptionCode', "return false;\n"),
-        templateValues.get('typedArraysAreStructs', False),
+        templateValues.get('spiderMonkeyInterfacesAreStructs', False),
         isConstructorRetval=templateValues.get('isConstructorRetval', False))[0]
 
     defaultValues = {'obj': 'obj'}
@@ -8193,10 +8205,10 @@ class CGMethodCall(CGThing):
             #     "object" arg.
 
             # First grab all the overloads that have a non-callback interface
-            # (which includes typed arrays and arraybuffers) at the
-            # distinguishing index.  We can also include the ones that have an
-            # "object" here, since if those are present no other object-typed
-            # argument will be.
+            # (which includes SpiderMonkey interfaces) at the distinguishing
+            # index.  We can also include the ones that have an "object" here,
+            # since if those are present no other object-typed argument will
+            # be.
             objectSigs = [
                 s for s in possibleSignatures
                 if (distinguishingType(s).isObject() or
@@ -8227,16 +8239,17 @@ class CGMethodCall(CGThing):
             # There might be more than one thing in objectSigs; we need to check
             # which ones we unwrap to.
             if len(objectSigs) > 0:
-                # Here it's enough to guard on our argument being an object. The
-                # code for unwrapping non-callback interfaces, typed arrays,
-                # sequences, and Dates will just bail out and move on to
-                # the next overload if the object fails to unwrap correctly,
-                # while "object" accepts any object anyway.  We could even not
-                # do the isObject() check up front here, but in cases where we
-                # have multiple object overloads it makes sense to do it only
-                # once instead of for each overload.  That will also allow the
-                # unwrapping test to skip having to do codegen for the
-                # null-or-undefined case, which we already handled above.
+                # Here it's enough to guard on our argument being an object.
+                # The code for unwrapping non-callback interfaces, spiderMonkey
+                # interfaces, sequences, and Dates will just bail out and move
+                # on to the next overload if the object fails to unwrap
+                # correctly, while "object" accepts any object anyway.  We
+                # could even not do the isObject() check up front here, but in
+                # cases where we have multiple object overloads it makes sense
+                # to do it only once instead of for each overload.  That will
+                # also allow the unwrapping test to skip having to do codegen
+                # for the null-or-undefined case, which we already handled
+                # above.
                 caseBody.append(CGGeneric("if (%s.isObject()) {\n" %
                                           distinguishingArg))
                 for sig in objectSigs:
@@ -10239,7 +10252,7 @@ class CGUnionStruct(CGThing):
                 "jsvalHandle": "rval",
                 "obj": "scopeObj",
                 "result": val,
-                "typedArraysAreStructs": True
+                "spiderMonkeyInterfacesAreStructs": True
             })
         return CGGeneric(wrapCode)
 
@@ -13219,7 +13232,7 @@ class CGDictionary(CGThing):
                 # 'obj' can just be allowed to be the string "obj", since that
                 # will be our dictionary object, which is presumably itself in
                 # the right scope.
-                'typedArraysAreStructs': True
+                'spiderMonkeyInterfacesAreStructs': True
             })
         conversion = CGGeneric(innerTemplate)
         conversion = CGWrapper(conversion,
@@ -13679,7 +13692,7 @@ class ForwardDeclarationBuilder:
             except NoSuchDescriptorError:
                 pass
 
-        # Note: Spidermonkey interfaces are typedefs, so can't be
+        # Note: SpiderMonkey interfaces are typedefs, so can't be
         # forward-declared
         elif t.isPromise():
             self.addInMozillaDom("Promise")
@@ -13988,7 +14001,7 @@ class CGBindingRoot(CGThing):
             return {desc.getDescriptor(desc.interface.parent.identifier.name)}
         for x in dependencySortObjects(jsImplemented, getParentDescriptor,
                                        lambda d: d.interface.identifier.name):
-            cgthings.append(CGCallbackInterface(x, typedArraysAreStructs=True))
+            cgthings.append(CGCallbackInterface(x, spiderMonkeyInterfacesAreStructs=True))
             cgthings.append(CGJSImplClass(x))
 
         # And make sure we have the right number of newlines at the end
@@ -14050,14 +14063,13 @@ class CGBindingRoot(CGThing):
 class CGNativeMember(ClassMethod):
     def __init__(self, descriptorProvider, member, name, signature, extendedAttrs,
                  breakAfter=True, passJSBitsAsNeeded=True, visibility="public",
-                 typedArraysAreStructs=True, variadicIsSequence=False,
-                 resultNotAddRefed=False,
-                 virtual=False,
-                 override=False):
+                 spiderMonkeyInterfacesAreStructs=True,
+                 variadicIsSequence=False, resultNotAddRefed=False,
+                 virtual=False, override=False):
         """
-        If typedArraysAreStructs is false, typed arrays will be passed as
-        JS::Handle<JSObject*>.  If it's true they will be passed as one of the
-        dom::TypedArray subclasses.
+        If spiderMonkeyInterfacesAreStructs is false, SpiderMonkey interfaces
+        will be passed as JS::Handle<JSObject*>.  If it's true they will be
+        passed as one of the dom::SpiderMonkeyInterfaceObjectStorage subclasses.
 
         If passJSBitsAsNeeded is false, we don't automatically pass in a
         JSContext* or a JSObject* based on the return and argument types.  We
@@ -14068,7 +14080,7 @@ class CGNativeMember(ClassMethod):
         self.extendedAttrs = extendedAttrs
         self.resultAlreadyAddRefed = not resultNotAddRefed
         self.passJSBitsAsNeeded = passJSBitsAsNeeded
-        self.typedArraysAreStructs = typedArraysAreStructs
+        self.spiderMonkeyInterfacesAreStructs = spiderMonkeyInterfacesAreStructs
         self.variadicIsSequence = variadicIsSequence
         breakAfterSelf = "\n" if breakAfter else ""
         ClassMethod.__init__(self, name,
@@ -14375,7 +14387,7 @@ class CGNativeMember(ClassMethod):
                     False, False)
 
         if type.isSpiderMonkeyInterface():
-            if not self.typedArraysAreStructs:
+            if not self.spiderMonkeyInterfacesAreStructs:
                 return "JS::Handle<JSObject*>", False, False
 
             # Unroll for the name, in case we're nullable.
@@ -15547,16 +15559,16 @@ class CGFastCallback(CGClass):
 
 
 class CGCallbackInterface(CGCallback):
-    def __init__(self, descriptor, typedArraysAreStructs=False):
+    def __init__(self, descriptor, spiderMonkeyInterfacesAreStructs=False):
         iface = descriptor.interface
         attrs = [m for m in iface.members if m.isAttr() and not m.isStatic()]
-        getters = [CallbackGetter(a, descriptor, typedArraysAreStructs)
+        getters = [CallbackGetter(a, descriptor, spiderMonkeyInterfacesAreStructs)
                    for a in attrs]
-        setters = [CallbackSetter(a, descriptor, typedArraysAreStructs)
+        setters = [CallbackSetter(a, descriptor, spiderMonkeyInterfacesAreStructs)
                    for a in attrs if not a.readonly]
         methods = [m for m in iface.members
                    if m.isMethod() and not m.isStatic() and not m.isIdentifierLess()]
-        methods = [CallbackOperation(m, sig, descriptor, typedArraysAreStructs)
+        methods = [CallbackOperation(m, sig, descriptor, spiderMonkeyInterfacesAreStructs)
                    for m in methods for sig in m.signatures()]
         if iface.isJSImplemented() and iface.ctor():
             sigs = descriptor.interface.ctor().signatures()
@@ -15601,7 +15613,8 @@ class CallbackMember(CGNativeMember):
     # CallSetup already handled the unmark-gray bits for us. we don't have
     # anything better to use for 'obj', really...
     def __init__(self, sig, name, descriptorProvider, needThisHandling,
-                 rethrowContentException=False, typedArraysAreStructs=False,
+                 rethrowContentException=False,
+                 spiderMonkeyInterfacesAreStructs=False,
                  wrapScope='CallbackKnownNotGray()'):
         """
         needThisHandling is True if we need to be able to accept a specified
@@ -15636,7 +15649,7 @@ class CallbackMember(CGNativeMember):
                                 extendedAttrs={},
                                 passJSBitsAsNeeded=False,
                                 visibility=visibility,
-                                typedArraysAreStructs=typedArraysAreStructs)
+                                spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs)
         # We have to do all the generation of our body now, because
         # the caller relies on us throwing if we can't manage it.
         self.exceptionCode = ("aRv.Throw(NS_ERROR_UNEXPECTED);\n"
@@ -15753,7 +15766,7 @@ class CallbackMember(CGNativeMember):
                     'obj': self.wrapScope,
                     'returnsNewObject': False,
                     'exceptionCode': self.exceptionCode,
-                    'typedArraysAreStructs': self.typedArraysAreStructs
+                    'spiderMonkeyInterfacesAreStructs': self.spiderMonkeyInterfacesAreStructs
                 })
         except MethodNotNewObjectError as err:
             raise TypeError("%s being passed as an argument to %s but is not "
@@ -15857,10 +15870,11 @@ class CallbackMember(CGNativeMember):
 
 class CallbackMethod(CallbackMember):
     def __init__(self, sig, name, descriptorProvider, needThisHandling,
-                 rethrowContentException=False, typedArraysAreStructs=False):
+                 rethrowContentException=False,
+                 spiderMonkeyInterfacesAreStructs=False):
         CallbackMember.__init__(self, sig, name, descriptorProvider,
                                 needThisHandling, rethrowContentException,
-                                typedArraysAreStructs=typedArraysAreStructs)
+                                spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs)
 
     def getRvalDecl(self):
         return "JS::Rooted<JS::Value> rval(cx, JS::UndefinedValue());\n"
@@ -15919,12 +15933,12 @@ class CallbackOperationBase(CallbackMethod):
     """
     def __init__(self, signature, jsName, nativeName, descriptor,
                  singleOperation, rethrowContentException=False,
-                 typedArraysAreStructs=False):
+                 spiderMonkeyInterfacesAreStructs=False):
         self.singleOperation = singleOperation
         self.methodName = descriptor.binaryNameFor(jsName)
         CallbackMethod.__init__(self, signature, nativeName, descriptor,
                                 singleOperation, rethrowContentException,
-                                typedArraysAreStructs=typedArraysAreStructs)
+                                spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs)
 
     def getThisDecl(self):
         if not self.singleOperation:
@@ -15975,7 +15989,8 @@ class CallbackOperation(CallbackOperationBase):
     """
     Codegen actual WebIDL operations on callback interfaces.
     """
-    def __init__(self, method, signature, descriptor, typedArraysAreStructs):
+    def __init__(self, method, signature, descriptor,
+                 spiderMonkeyInterfacesAreStructs):
         self.ensureASCIIName(method)
         self.method = method
         jsName = method.identifier.name
@@ -15984,7 +15999,7 @@ class CallbackOperation(CallbackOperationBase):
                                        MakeNativeName(descriptor.binaryNameFor(jsName)),
                                        descriptor, descriptor.interface.isSingleOperationInterface(),
                                        rethrowContentException=descriptor.interface.isJSImplemented(),
-                                       typedArraysAreStructs=typedArraysAreStructs)
+                                       spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs)
 
     def getPrettyName(self):
         return "%s.%s" % (self.descriptorProvider.interface.identifier.name,
@@ -15995,13 +16010,14 @@ class CallbackAccessor(CallbackMember):
     """
     Shared superclass for CallbackGetter and CallbackSetter.
     """
-    def __init__(self, attr, sig, name, descriptor, typedArraysAreStructs):
+    def __init__(self, attr, sig, name, descriptor,
+                 spiderMonkeyInterfacesAreStructs):
         self.ensureASCIIName(attr)
         self.attrName = attr.identifier.name
         CallbackMember.__init__(self, sig, name, descriptor,
                                 needThisHandling=False,
                                 rethrowContentException=descriptor.interface.isJSImplemented(),
-                                typedArraysAreStructs=typedArraysAreStructs)
+                                spiderMonkeyInterfacesAreStructs=spiderMonkeyInterfacesAreStructs)
 
     def getPrettyName(self):
         return "%s.%s" % (self.descriptorProvider.interface.identifier.name,
@@ -16009,12 +16025,12 @@ class CallbackAccessor(CallbackMember):
 
 
 class CallbackGetter(CallbackAccessor):
-    def __init__(self, attr, descriptor, typedArraysAreStructs):
+    def __init__(self, attr, descriptor, spiderMonkeyInterfacesAreStructs):
         CallbackAccessor.__init__(self, attr,
                                   (attr.type, []),
                                   callbackGetterName(attr, descriptor),
                                   descriptor,
-                                  typedArraysAreStructs)
+                                  spiderMonkeyInterfacesAreStructs)
 
     def getRvalDecl(self):
         return "JS::Rooted<JS::Value> rval(cx, JS::UndefinedValue());\n"
@@ -16036,12 +16052,12 @@ class CallbackGetter(CallbackAccessor):
 
 
 class CallbackSetter(CallbackAccessor):
-    def __init__(self, attr, descriptor, typedArraysAreStructs):
+    def __init__(self, attr, descriptor, spiderMonkeyInterfacesAreStructs):
         CallbackAccessor.__init__(self, attr,
                                   (BuiltinTypes[IDLBuiltinType.Types.void],
                                    [FakeArgument(attr.type, attr)]),
                                   callbackSetterName(attr, descriptor),
-                                  descriptor, typedArraysAreStructs)
+                                  descriptor, spiderMonkeyInterfacesAreStructs)
 
     def getRvalDecl(self):
         # We don't need an rval
@@ -16076,7 +16092,7 @@ class CGJSImplInitOperation(CallbackOperationBase):
                                        "__init", "__Init", descriptor,
                                        singleOperation=False,
                                        rethrowContentException=True,
-                                       typedArraysAreStructs=True)
+                                       spiderMonkeyInterfacesAreStructs=True)
 
     def getPrettyName(self):
         return "__init"
diff --git a/dom/bindings/ReadableStream.h b/dom/bindings/ReadableStream.h
new file mode 100644
index 0000000000..1ea7ac4d88
--- /dev/null
+++ b/dom/bindings/ReadableStream.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_ReadableStream_h
+#define mozilla_dom_ReadableStream_h
+
+#include "mozilla/dom/SpiderMonkeyInterface.h"
+
+namespace mozilla {
+namespace dom {
+
+struct ReadableStream : public SpiderMonkeyInterfaceObjectStorage
+{
+  inline bool Init(JSObject* obj)
+  {
+    MOZ_ASSERT(!inited());
+    mImplObj = mWrappedObj = js::UnwrapReadableStream(obj);
+    return inited();
+  }
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif /* mozilla_dom_ReadableStream_h */
diff --git a/dom/bindings/SpiderMonkeyInterface.h b/dom/bindings/SpiderMonkeyInterface.h
new file mode 100644
index 0000000000..f852afddaf
--- /dev/null
+++ b/dom/bindings/SpiderMonkeyInterface.h
@@ -0,0 +1,144 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_SpiderMonkeyInterface_h
+#define mozilla_dom_SpiderMonkeyInterface_h
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "js/TracingAPI.h"
+
+namespace mozilla {
+namespace dom {
+
+/*
+ * Class that just handles the JSObject storage and tracing for spidermonkey
+ * interfaces
+ */
+struct SpiderMonkeyInterfaceObjectStorage
+{
+protected:
+  JSObject* mImplObj;
+  JSObject* mWrappedObj;
+
+  SpiderMonkeyInterfaceObjectStorage()
+    : mImplObj(nullptr),
+      mWrappedObj(nullptr)
+  {
+  }
+
+  SpiderMonkeyInterfaceObjectStorage(SpiderMonkeyInterfaceObjectStorage&& aOther)
+    : mImplObj(aOther.mImplObj),
+      mWrappedObj(aOther.mWrappedObj)
+  {
+    aOther.mImplObj = nullptr;
+    aOther.mWrappedObj = nullptr;
+  }
+
+public:
+  inline void TraceSelf(JSTracer* trc)
+  {
+    JS::UnsafeTraceRoot(trc, &mImplObj, "SpiderMonkeyInterfaceObjectStorage.mImplObj");
+    JS::UnsafeTraceRoot(trc, &mWrappedObj, "SpiderMonkeyInterfaceObjectStorage.mWrappedObj");
+  }
+
+  inline bool inited() const
+  {
+    return !!mImplObj;
+  }
+
+  inline bool WrapIntoNewCompartment(JSContext* cx)
+  {
+    return JS_WrapObject(cx,
+      JS::MutableHandle<JSObject*>::fromMarkedLocation(&mWrappedObj));
+  }
+
+  inline JSObject *Obj() const
+  {
+    MOZ_ASSERT(inited());
+    return mWrappedObj;
+  }
+
+private:
+  SpiderMonkeyInterfaceObjectStorage(const SpiderMonkeyInterfaceObjectStorage&) = delete;
+};
+
+// A class for rooting an existing SpiderMonkey Interface struct
+template<typename InterfaceType>
+class MOZ_RAII SpiderMonkeyInterfaceRooter : private JS::CustomAutoRooter
+{
+public:
+  template <typename CX>
+  SpiderMonkeyInterfaceRooter(const CX& cx,
+                              InterfaceType* aInterface MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
+      mInterface(aInterface)
+  {
+  }
+
+  virtual void trace(JSTracer* trc) override
+  {
+    mInterface->TraceSelf(trc);
+  }
+
+private:
+  SpiderMonkeyInterfaceObjectStorage* const mInterface;
+};
+
+// And a specialization for dealing with nullable SpiderMonkey interfaces
+template<typename Inner> struct Nullable;
+template<typename InterfaceType>
+class MOZ_RAII SpiderMonkeyInterfaceRooter<Nullable<InterfaceType>> :
+    private JS::CustomAutoRooter
+{
+public:
+  template <typename CX>
+  SpiderMonkeyInterfaceRooter(const CX& cx,
+                              Nullable<InterfaceType>* aInterface MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
+      mInterface(aInterface)
+  {
+  }
+
+  virtual void trace(JSTracer* trc) override
+  {
+    if (!mInterface->IsNull()) {
+      mInterface->Value().TraceSelf(trc);
+    }
+  }
+
+private:
+  Nullable<InterfaceType>* const mInterface;
+};
+
+// Class for easily setting up a rooted SpiderMonkey interface object on the
+// stack
+template<typename InterfaceType>
+class MOZ_RAII RootedSpiderMonkeyInterface final : public InterfaceType,
+                                                   private SpiderMonkeyInterfaceRooter<InterfaceType>
+{
+public:
+  template <typename CX>
+  explicit RootedSpiderMonkeyInterface(const CX& cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : InterfaceType(),
+      SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this
+                                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
+  {
+  }
+
+  template <typename CX>
+  RootedSpiderMonkeyInterface(const CX& cx, JSObject* obj MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : InterfaceType(obj),
+      SpiderMonkeyInterfaceRooter<InterfaceType>(cx, this
+                                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
+  {
+  }
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif /* mozilla_dom_SpiderMonkeyInterface_h */
diff --git a/dom/bindings/TypedArray.h b/dom/bindings/TypedArray.h
index 631707579b..8de0621d46 100644
--- a/dom/bindings/TypedArray.h
+++ b/dom/bindings/TypedArray.h
@@ -6,52 +6,16 @@
 #ifndef mozilla_dom_TypedArray_h
 #define mozilla_dom_TypedArray_h
 
-#include "jsapi.h"
-#include "jsfriendapi.h"
-#include "js/RootingAPI.h"
-#include "js/TracingAPI.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Move.h"
 #include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/SpiderMonkeyInterface.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
 namespace dom {
 
 /*
- * Class that just handles the JSObject storage and tracing for typed arrays
- */
-struct TypedArrayObjectStorage : AllTypedArraysBase {
-protected:
-  JSObject* mTypedObj;
-  JSObject* mWrappedObj;
-
-  TypedArrayObjectStorage()
-    : mTypedObj(nullptr),
-      mWrappedObj(nullptr)
-  {
-  }
-
-  TypedArrayObjectStorage(TypedArrayObjectStorage&& aOther)
-    : mTypedObj(aOther.mTypedObj),
-      mWrappedObj(aOther.mWrappedObj)
-  {
-    aOther.mTypedObj = nullptr;
-    aOther.mWrappedObj = nullptr;
-  }
-
-public:
-  inline void TraceSelf(JSTracer* trc)
-  {
-    JS::UnsafeTraceRoot(trc, &mTypedObj, "TypedArray.mTypedObj");
-    JS::UnsafeTraceRoot(trc, &mWrappedObj, "TypedArray.mWrappedObj");
-  }
-
-private:
-  TypedArrayObjectStorage(const TypedArrayObjectStorage&) = delete;
-};
-
-/*
  * Various typed array classes for argument conversion.  We have a base class
  * that has a way of initializing a TypedArray from an existing typed array, and
  * a subclass of the base class that supports creation of a relevant typed array
@@ -60,7 +24,9 @@ private:
 template<typename T,
          JSObject* UnwrapArray(JSObject*),
          void GetLengthAndDataAndSharedness(JSObject*, uint32_t*, bool*, T**)>
-struct TypedArray_base : public TypedArrayObjectStorage {
+struct TypedArray_base : public SpiderMonkeyInterfaceObjectStorage,
+                         AllTypedArraysBase
+{
   typedef T element_type;
 
   TypedArray_base()
@@ -72,7 +38,7 @@ struct TypedArray_base : public TypedArrayObjectStorage {
   }
 
   TypedArray_base(TypedArray_base&& aOther)
-    : TypedArrayObjectStorage(Move(aOther)),
+    : SpiderMonkeyInterfaceObjectStorage(Move(aOther)),
       mData(aOther.mData),
       mLength(aOther.mLength),
       mShared(aOther.mShared),
@@ -94,14 +60,10 @@ public:
   inline bool Init(JSObject* obj)
   {
     MOZ_ASSERT(!inited());
-    mTypedObj = mWrappedObj = UnwrapArray(obj);
+    mImplObj = mWrappedObj = UnwrapArray(obj);
     return inited();
   }
 
-  inline bool inited() const {
-    return !!mTypedObj;
-  }
-
   // About shared memory:
   //
   // Any DOM TypedArray as well as any DOM ArrayBufferView that does
@@ -173,22 +135,11 @@ public:
     return mLength;
   }
 
-  inline JSObject *Obj() const {
-    MOZ_ASSERT(inited());
-    return mWrappedObj;
-  }
-
-  inline bool WrapIntoNewCompartment(JSContext* cx)
-  {
-    return JS_WrapObject(cx,
-      JS::MutableHandle<JSObject*>::fromMarkedLocation(&mWrappedObj));
-  }
-
   inline void ComputeLengthAndData() const
   {
     MOZ_ASSERT(inited());
     MOZ_ASSERT(!mComputed);
-    GetLengthAndDataAndSharedness(mTypedObj, &mLength, &mShared, &mData);
+    GetLengthAndDataAndSharedness(mImplObj, &mLength, &mShared, &mData);
     mComputed = true;
   }
 
@@ -363,77 +314,6 @@ class TypedArrayCreator
     const ArrayType& mArray;
 };
 
-// A class for rooting an existing TypedArray struct
-template<typename ArrayType>
-class MOZ_RAII TypedArrayRooter : private JS::CustomAutoRooter
-{
-public:
-  template <typename CX>
-  TypedArrayRooter(const CX& cx,
-                   ArrayType* aArray MOZ_GUARD_OBJECT_NOTIFIER_PARAM) :
-    JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
-    mArray(aArray)
-  {
-  }
-
-  virtual void trace(JSTracer* trc) override
-  {
-    mArray->TraceSelf(trc);
-  }
-
-private:
-  TypedArrayObjectStorage* const mArray;
-};
-
-// And a specialization for dealing with nullable typed arrays
-template<typename Inner> struct Nullable;
-template<typename ArrayType>
-class MOZ_RAII TypedArrayRooter<Nullable<ArrayType> > :
-    private JS::CustomAutoRooter
-{
-public:
-  template <typename CX>
-  TypedArrayRooter(const CX& cx,
-                   Nullable<ArrayType>* aArray MOZ_GUARD_OBJECT_NOTIFIER_PARAM) :
-    JS::CustomAutoRooter(cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT),
-    mArray(aArray)
-  {
-  }
-
-  virtual void trace(JSTracer* trc) override
-  {
-    if (!mArray->IsNull()) {
-      mArray->Value().TraceSelf(trc);
-    }
-  }
-
-private:
-  Nullable<ArrayType>* const mArray;
-};
-
-// Class for easily setting up a rooted typed array object on the stack
-template<typename ArrayType>
-class MOZ_RAII RootedTypedArray final : public ArrayType,
-                                        private TypedArrayRooter<ArrayType>
-{
-public:
-  template <typename CX>
-  explicit RootedTypedArray(const CX& cx MOZ_GUARD_OBJECT_NOTIFIER_PARAM) :
-    ArrayType(),
-    TypedArrayRooter<ArrayType>(cx, this
-                                MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
-  {
-  }
-
-  template <typename CX>
-  RootedTypedArray(const CX& cx, JSObject* obj MOZ_GUARD_OBJECT_NOTIFIER_PARAM) :
-    ArrayType(obj),
-    TypedArrayRooter<ArrayType>(cx, this
-                                MOZ_GUARD_OBJECT_NOTIFIER_PARAM_TO_PARENT)
-  {
-  }
-};
-
 } // namespace dom
 } // namespace mozilla
 
diff --git a/dom/bindings/moz.build b/dom/bindings/moz.build
index 9afaf4fd45..60309080e4 100644
--- a/dom/bindings/moz.build
+++ b/dom/bindings/moz.build
@@ -38,9 +38,11 @@ EXPORTS.mozilla.dom += [
     'NonRefcountedDOMObject.h',
     'Nullable.h',
     'PrimitiveConversions.h',
+    'ReadableStream.h',
     'Record.h',
     'RootedDictionary.h',
     'SimpleGlobalObject.h',
+    'SpiderMonkeyInterface.h',
     'StructuredClone.h',
     'ToJSValue.h',
     'TypedArray.h',
diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index 59db43f6bd..0aa3afa4e8 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -2054,6 +2054,9 @@ class IDLType(IDLObject):
     def isRecord(self):
         return False
 
+    def isReadableStream(self):
+        return False
+
     def isArrayBuffer(self):
         return False
 
@@ -2081,12 +2084,12 @@ class IDLType(IDLObject):
 
     def isSpiderMonkeyInterface(self):
         """ Returns a boolean indicating whether this type is an 'interface'
-            type that is implemented in Spidermonkey.  At the moment, this
-            only returns true for the types from the TypedArray spec. """
+            type that is implemented in SpiderMonkey. """
         return self.isInterface() and (self.isArrayBuffer() or
                                        self.isArrayBufferView() or
                                        self.isSharedArrayBuffer() or
-                                       self.isTypedArray())
+                                       self.isTypedArray() or
+                                       self.isReadableStream())
 
     def isDictionary(self):
         return False
@@ -2275,6 +2278,9 @@ class IDLNullableType(IDLParameterizedType):
     def isRecord(self):
         return self.inner.isRecord()
 
+    def isReadableStream(self):
+        return self.inner.isReadableStream()
+
     def isArrayBuffer(self):
         return self.inner.isArrayBuffer()
 
@@ -2634,6 +2640,9 @@ class IDLTypedefType(IDLType):
     def isRecord(self):
         return self.inner.isRecord()
 
+    def isReadableStream(self):
+        return self.inner.isReadableStream()
+
     def isDictionary(self):
         return self.inner.isDictionary()
 
@@ -2945,7 +2954,8 @@ class IDLBuiltinType(IDLType):
         'Int32Array',
         'Uint32Array',
         'Float32Array',
-        'Float64Array'
+        'Float64Array',
+        'ReadableStream',
         )
 
     TagLookup = {
@@ -2980,7 +2990,8 @@ class IDLBuiltinType(IDLType):
         Types.Int32Array: IDLType.Tags.interface,
         Types.Uint32Array: IDLType.Tags.interface,
         Types.Float32Array: IDLType.Tags.interface,
-        Types.Float64Array: IDLType.Tags.interface
+        Types.Float64Array: IDLType.Tags.interface,
+        Types.ReadableStream: IDLType.Tags.interface,
     }
 
     def __init__(self, location, name, type):
@@ -3027,6 +3038,9 @@ class IDLBuiltinType(IDLType):
         return (self._typeTag >= IDLBuiltinType.Types.Int8Array and
                 self._typeTag <= IDLBuiltinType.Types.Float64Array)
 
+    def isReadableStream(self):
+        return self._typeTag == IDLBuiltinType.Types.ReadableStream
+
     def isInterface(self):
         # TypedArray things are interface types per the TypedArray spec,
         # but we handle them as builtins because SpiderMonkey implements
@@ -3034,7 +3048,8 @@ class IDLBuiltinType(IDLType):
         return (self.isArrayBuffer() or
                 self.isArrayBufferView() or
                 self.isSharedArrayBuffer() or
-                self.isTypedArray())
+                self.isTypedArray() or
+                self.isReadableStream())
 
     def isNonCallbackInterface(self):
         # All the interfaces we can be are non-callback
@@ -3104,6 +3119,7 @@ class IDLBuiltinType(IDLType):
                  # that's not an ArrayBuffer or a callback interface
                  (self.isArrayBuffer() and not other.isArrayBuffer()) or
                  (self.isSharedArrayBuffer() and not other.isSharedArrayBuffer()) or
+                 (self.isReadableStream() and not other.isReadableStream()) or
                  # ArrayBufferView is distinguishable from everything
                  # that's not an ArrayBufferView or typed array.
                  (self.isArrayBufferView() and not other.isArrayBufferView() and
@@ -3213,7 +3229,10 @@ BuiltinTypes = {
                        IDLBuiltinType.Types.Float32Array),
     IDLBuiltinType.Types.Float64Array:
         IDLBuiltinType(BuiltinLocation("<builtin type>"), "Float64Array",
-                       IDLBuiltinType.Types.Float64Array)
+                       IDLBuiltinType.Types.Float64Array),
+    IDLBuiltinType.Types.ReadableStream:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "ReadableStream",
+                       IDLBuiltinType.Types.ReadableStream),
 }
 
 
@@ -5232,7 +5251,8 @@ class Tokenizer(object):
         "maplike": "MAPLIKE",
         "setlike": "SETLIKE",
         "iterable": "ITERABLE",
-        "namespace": "NAMESPACE"
+        "namespace": "NAMESPACE",
+        "ReadableStream": "READABLESTREAM",
         }
 
     tokens.extend(keywords.values())
@@ -6420,6 +6440,7 @@ class Parser(Tokenizer):
             NonAnyType : PrimitiveType Null
                        | ARRAYBUFFER Null
                        | SHAREDARRAYBUFFER Null
+                       | READABLESTREAM Null
                        | OBJECT Null
         """
         if p[1] == "object":
@@ -6428,6 +6449,8 @@ class Parser(Tokenizer):
             type = BuiltinTypes[IDLBuiltinType.Types.ArrayBuffer]
         elif p[1] == "SharedArrayBuffer":
             type = BuiltinTypes[IDLBuiltinType.Types.SharedArrayBuffer]
+        elif p[1] == "ReadableStream":
+            type = BuiltinTypes[IDLBuiltinType.Types.ReadableStream]
         else:
             type = BuiltinTypes[p[1]]
 
diff --git a/dom/cache/AutoUtils.cpp b/dom/cache/AutoUtils.cpp
index d1f354336e..bfa4cffd23 100644
--- a/dom/cache/AutoUtils.cpp
+++ b/dom/cache/AutoUtils.cpp
@@ -289,9 +289,9 @@ MatchInPutList(InternalRequest* aRequest,
 } // namespace
 
 void
-AutoChildOpArgs::Add(InternalRequest* aRequest, BodyAction aBodyAction,
-                     SchemeAction aSchemeAction, Response& aResponse,
-                     ErrorResult& aRv)
+AutoChildOpArgs::Add(JSContext* aCx, InternalRequest* aRequest,
+                     BodyAction aBodyAction, SchemeAction aSchemeAction,
+                     Response& aResponse, ErrorResult& aRv)
 {
   MOZ_DIAGNOSTIC_ASSERT(!mSent);
 
@@ -329,7 +329,7 @@ AutoChildOpArgs::Add(InternalRequest* aRequest, BodyAction aBodyAction,
       mTypeUtils->ToCacheRequest(pair.request(), aRequest, aBodyAction,
                                  aSchemeAction, mStreamCleanupList, aRv);
       if (!aRv.Failed()) {
-        mTypeUtils->ToCacheResponse(pair.response(), aResponse,
+        mTypeUtils->ToCacheResponse(aCx, pair.response(), aResponse,
                                     mStreamCleanupList, aRv);
       }
 
diff --git a/dom/cache/AutoUtils.h b/dom/cache/AutoUtils.h
index 244639f7c0..188c9d74e3 100644
--- a/dom/cache/AutoUtils.h
+++ b/dom/cache/AutoUtils.h
@@ -55,7 +55,7 @@ public:
 
   void Add(InternalRequest* aRequest, BodyAction aBodyAction,
            SchemeAction aSchemeAction, ErrorResult& aRv);
-  void Add(InternalRequest* aRequest, BodyAction aBodyAction,
+  void Add(JSContext* aCx, InternalRequest* aRequest, BodyAction aBodyAction,
            SchemeAction aSchemeAction, Response& aResponse, ErrorResult& aRv);
 
   const CacheOpArgs& SendAsOpArgs();
diff --git a/dom/cache/Cache.cpp b/dom/cache/Cache.cpp
index 60e4f76b92..dd142881ec 100644
--- a/dom/cache/Cache.cpp
+++ b/dom/cache/Cache.cpp
@@ -184,7 +184,10 @@ public:
 
     // Now store the unwrapped Response list in the Cache.
     ErrorResult result;
-    RefPtr<Promise> put = mCache->PutAll(mRequestList, responseList, result);
+    // TODO: Here we use the JSContext as received by the ResolvedCallback, and
+    // its state could be the wrong one. The spec doesn't say anything
+    // about it, yet (bug 1384006)
+    RefPtr<Promise> put = mCache->PutAll(aCx, mRequestList, responseList, result);
     if (NS_WARN_IF(result.Failed())) {
       // TODO: abort the fetch requests we have running (bug 1157434)
       mPromise->MaybeReject(result);
@@ -245,7 +248,7 @@ Cache::Cache(nsIGlobalObject* aGlobal, CacheChild* aActor)
 }
 
 already_AddRefed<Promise>
-Cache::Match(const RequestOrUSVString& aRequest,
+Cache::Match(JSContext* aCx, const RequestOrUSVString& aRequest,
              const CacheQueryOptions& aOptions, ErrorResult& aRv)
 {
   if (NS_WARN_IF(!mActor)) {
@@ -255,7 +258,8 @@ Cache::Match(const RequestOrUSVString& aRequest,
 
   CacheChild::AutoLock actorLock(mActor);
 
-  RefPtr<InternalRequest> ir = ToInternalRequest(aRequest, IgnoreBody, aRv);
+  RefPtr<InternalRequest> ir =
+    ToInternalRequest(aCx, aRequest, IgnoreBody, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
@@ -274,7 +278,7 @@ Cache::Match(const RequestOrUSVString& aRequest,
 }
 
 already_AddRefed<Promise>
-Cache::MatchAll(const Optional<RequestOrUSVString>& aRequest,
+Cache::MatchAll(JSContext* aCx, const Optional<RequestOrUSVString>& aRequest,
                 const CacheQueryOptions& aOptions, ErrorResult& aRv)
 {
   if (NS_WARN_IF(!mActor)) {
@@ -290,8 +294,8 @@ Cache::MatchAll(const Optional<RequestOrUSVString>& aRequest,
   AutoChildOpArgs args(this, CacheMatchAllArgs(void_t(), params), 1);
 
   if (aRequest.WasPassed()) {
-    RefPtr<InternalRequest> ir = ToInternalRequest(aRequest.Value(),
-                                                     IgnoreBody, aRv);
+    RefPtr<InternalRequest> ir = ToInternalRequest(aCx, aRequest.Value(),
+                                                   IgnoreBody, aRv);
     if (aRv.Failed()) {
       return nullptr;
     }
@@ -390,8 +394,8 @@ Cache::AddAll(JSContext* aContext,
 }
 
 already_AddRefed<Promise>
-Cache::Put(const RequestOrUSVString& aRequest, Response& aResponse,
-           ErrorResult& aRv)
+Cache::Put(JSContext* aCx, const RequestOrUSVString& aRequest,
+           Response& aResponse, ErrorResult& aRv)
 {
   if (NS_WARN_IF(!mActor)) {
     aRv.Throw(NS_ERROR_UNEXPECTED);
@@ -404,14 +408,14 @@ Cache::Put(const RequestOrUSVString& aRequest, Response& aResponse,
     return nullptr;
   }
 
-  RefPtr<InternalRequest> ir = ToInternalRequest(aRequest, ReadBody, aRv);
+  RefPtr<InternalRequest> ir = ToInternalRequest(aCx, aRequest, ReadBody, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
 
   AutoChildOpArgs args(this, CachePutAllArgs(), 1);
 
-  args.Add(ir, ReadBody, TypeErrorOnInvalidScheme,
+  args.Add(aCx, ir, ReadBody, TypeErrorOnInvalidScheme,
            aResponse, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
@@ -421,7 +425,7 @@ Cache::Put(const RequestOrUSVString& aRequest, Response& aResponse,
 }
 
 already_AddRefed<Promise>
-Cache::Delete(const RequestOrUSVString& aRequest,
+Cache::Delete(JSContext* aCx, const RequestOrUSVString& aRequest,
               const CacheQueryOptions& aOptions, ErrorResult& aRv)
 {
   if (NS_WARN_IF(!mActor)) {
@@ -431,7 +435,8 @@ Cache::Delete(const RequestOrUSVString& aRequest,
 
   CacheChild::AutoLock actorLock(mActor);
 
-  RefPtr<InternalRequest> ir = ToInternalRequest(aRequest, IgnoreBody, aRv);
+  RefPtr<InternalRequest> ir =
+    ToInternalRequest(aCx, aRequest, IgnoreBody, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
@@ -450,7 +455,7 @@ Cache::Delete(const RequestOrUSVString& aRequest,
 }
 
 already_AddRefed<Promise>
-Cache::Keys(const Optional<RequestOrUSVString>& aRequest,
+Cache::Keys(JSContext* aCx, const Optional<RequestOrUSVString>& aRequest,
             const CacheQueryOptions& aOptions, ErrorResult& aRv)
 {
   if (NS_WARN_IF(!mActor)) {
@@ -466,8 +471,8 @@ Cache::Keys(const Optional<RequestOrUSVString>& aRequest,
   AutoChildOpArgs args(this, CacheKeysArgs(void_t(), params), 1);
 
   if (aRequest.WasPassed()) {
-    RefPtr<InternalRequest> ir = ToInternalRequest(aRequest.Value(),
-                                                     IgnoreBody, aRv);
+    RefPtr<InternalRequest> ir =
+      ToInternalRequest(aCx, aRequest.Value(), IgnoreBody, aRv);
     if (NS_WARN_IF(aRv.Failed())) {
       return nullptr;
     }
@@ -627,7 +632,7 @@ Cache::AddAll(const GlobalObject& aGlobal,
 }
 
 already_AddRefed<Promise>
-Cache::PutAll(const nsTArray<RefPtr<Request>>& aRequestList,
+Cache::PutAll(JSContext* aCx, const nsTArray<RefPtr<Request>>& aRequestList,
               const nsTArray<RefPtr<Response>>& aResponseList,
               ErrorResult& aRv)
 {
@@ -644,7 +649,8 @@ Cache::PutAll(const nsTArray<RefPtr<Request>>& aRequestList,
 
   for (uint32_t i = 0; i < aRequestList.Length(); ++i) {
     RefPtr<InternalRequest> ir = aRequestList[i]->GetInternalRequest();
-    args.Add(ir, ReadBody, TypeErrorOnInvalidScheme, *aResponseList[i], aRv);
+    args.Add(aCx, ir, ReadBody, TypeErrorOnInvalidScheme, *aResponseList[i],
+             aRv);
     if (NS_WARN_IF(aRv.Failed())) {
       return nullptr;
     }
diff --git a/dom/cache/Cache.h b/dom/cache/Cache.h
index 04f891dca5..6fea3d36a0 100644
--- a/dom/cache/Cache.h
+++ b/dom/cache/Cache.h
@@ -43,10 +43,10 @@ public:
 
   // webidl interface methods
   already_AddRefed<Promise>
-  Match(const RequestOrUSVString& aRequest, const CacheQueryOptions& aOptions,
-        ErrorResult& aRv);
+  Match(JSContext* aCx, const RequestOrUSVString& aRequest,
+        const CacheQueryOptions& aOptions, ErrorResult& aRv);
   already_AddRefed<Promise>
-  MatchAll(const Optional<RequestOrUSVString>& aRequest,
+  MatchAll(JSContext* aCx, const Optional<RequestOrUSVString>& aRequest,
            const CacheQueryOptions& aOptions, ErrorResult& aRv);
   already_AddRefed<Promise>
   Add(JSContext* aContext, const RequestOrUSVString& aRequest,
@@ -55,13 +55,13 @@ public:
   AddAll(JSContext* aContext,
          const Sequence<OwningRequestOrUSVString>& aRequests, ErrorResult& aRv);
   already_AddRefed<Promise>
-  Put(const RequestOrUSVString& aRequest, Response& aResponse,
+  Put(JSContext* aCx, const RequestOrUSVString& aRequest, Response& aResponse,
       ErrorResult& aRv);
   already_AddRefed<Promise>
-  Delete(const RequestOrUSVString& aRequest, const CacheQueryOptions& aOptions,
-         ErrorResult& aRv);
+  Delete(JSContext* aCx, const RequestOrUSVString& aRequest,
+         const CacheQueryOptions& aOptions, ErrorResult& aRv);
   already_AddRefed<Promise>
-  Keys(const Optional<RequestOrUSVString>& aRequest,
+  Keys(JSContext* aCx, const Optional<RequestOrUSVString>& aRequest,
        const CacheQueryOptions& aParams, ErrorResult& aRv);
 
   // binding methods
@@ -100,7 +100,7 @@ private:
          ErrorResult& aRv);
 
   already_AddRefed<Promise>
-  PutAll(const nsTArray<RefPtr<Request>>& aRequestList,
+  PutAll(JSContext* aCx, const nsTArray<RefPtr<Request>>& aRequestList,
          const nsTArray<RefPtr<Response>>& aResponseList,
          ErrorResult& aRv);
 
diff --git a/dom/cache/CacheOpChild.cpp b/dom/cache/CacheOpChild.cpp
index 492c205ffc..9dc8997c26 100644
--- a/dom/cache/CacheOpChild.cpp
+++ b/dom/cache/CacheOpChild.cpp
@@ -74,7 +74,11 @@ CacheOpChild::CacheOpChild(CacheWorkerHolder* aWorkerHolder,
   MOZ_DIAGNOSTIC_ASSERT(mPromise);
 
   MOZ_ASSERT_IF(!NS_IsMainThread(), aWorkerHolder);
-  SetWorkerHolder(aWorkerHolder);
+  RefPtr<CacheWorkerHolder> workerHolder =
+    CacheWorkerHolder::PreferBehavior(aWorkerHolder,
+                                      CacheWorkerHolder::PreventIdleShutdownStart);
+
+  SetWorkerHolder(workerHolder);
 }
 
 CacheOpChild::~CacheOpChild()
@@ -165,7 +169,11 @@ CacheOpChild::Recv__delete__(const ErrorResult& aRv,
         break;
       }
 
-      actor->SetWorkerHolder(GetWorkerHolder());
+      RefPtr<CacheWorkerHolder> workerHolder =
+        CacheWorkerHolder::PreferBehavior(GetWorkerHolder(),
+                                          CacheWorkerHolder::AllowIdleShutdownStart);
+
+      actor->SetWorkerHolder(workerHolder);
       RefPtr<Cache> cache = new Cache(mGlobal, actor);
       mPromise->MaybeResolve(cache);
       break;
diff --git a/dom/cache/CacheStorage.cpp b/dom/cache/CacheStorage.cpp
index 2dae0b157d..05df8ddc69 100644
--- a/dom/cache/CacheStorage.cpp
+++ b/dom/cache/CacheStorage.cpp
@@ -204,7 +204,8 @@ CacheStorage::CreateOnWorker(Namespace aNamespace, nsIGlobalObject* aGlobal,
   }
 
   RefPtr<CacheWorkerHolder> workerHolder =
-    CacheWorkerHolder::Create(aWorkerPrivate);
+    CacheWorkerHolder::Create(aWorkerPrivate,
+                              CacheWorkerHolder::AllowIdleShutdownStart);
   if (!workerHolder) {
     NS_WARNING("Worker thread is shutting down.");
     aRv.Throw(NS_ERROR_FAILURE);
@@ -315,7 +316,7 @@ CacheStorage::CacheStorage(nsresult aFailureResult)
 }
 
 already_AddRefed<Promise>
-CacheStorage::Match(const RequestOrUSVString& aRequest,
+CacheStorage::Match(JSContext* aCx, const RequestOrUSVString& aRequest,
                     const CacheQueryOptions& aOptions, ErrorResult& aRv)
 {
   NS_ASSERT_OWNINGTHREAD(CacheStorage);
@@ -325,8 +326,8 @@ CacheStorage::Match(const RequestOrUSVString& aRequest,
     return nullptr;
   }
 
-  RefPtr<InternalRequest> request = ToInternalRequest(aRequest, IgnoreBody,
-                                                        aRv);
+  RefPtr<InternalRequest> request =
+    ToInternalRequest(aCx, aRequest, IgnoreBody, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
diff --git a/dom/cache/CacheStorage.h b/dom/cache/CacheStorage.h
index 04a2fa0dd9..c1cef4b428 100644
--- a/dom/cache/CacheStorage.h
+++ b/dom/cache/CacheStorage.h
@@ -59,9 +59,9 @@ public:
   DefineCaches(JSContext* aCx, JS::Handle<JSObject*> aGlobal);
 
   // webidl interface methods
-  already_AddRefed<Promise> Match(const RequestOrUSVString& aRequest,
-                                  const CacheQueryOptions& aOptions,
-                                  ErrorResult& aRv);
+  already_AddRefed<Promise>
+  Match(JSContext* aCx, const RequestOrUSVString& aRequest,
+        const CacheQueryOptions& aOptions, ErrorResult& aRv);
   already_AddRefed<Promise> Has(const nsAString& aKey, ErrorResult& aRv);
   already_AddRefed<Promise> Open(const nsAString& aKey, ErrorResult& aRv);
   already_AddRefed<Promise> Delete(const nsAString& aKey, ErrorResult& aRv);
diff --git a/dom/cache/CacheWorkerHolder.cpp b/dom/cache/CacheWorkerHolder.cpp
index 4ac97cbcab..1fd78553ee 100644
--- a/dom/cache/CacheWorkerHolder.cpp
+++ b/dom/cache/CacheWorkerHolder.cpp
@@ -18,11 +18,11 @@ using mozilla::dom::workers::WorkerPrivate;
 
 // static
 already_AddRefed<CacheWorkerHolder>
-CacheWorkerHolder::Create(WorkerPrivate* aWorkerPrivate)
+CacheWorkerHolder::Create(WorkerPrivate* aWorkerPrivate, Behavior aBehavior)
 {
   MOZ_DIAGNOSTIC_ASSERT(aWorkerPrivate);
 
-  RefPtr<CacheWorkerHolder> workerHolder = new CacheWorkerHolder();
+  RefPtr<CacheWorkerHolder> workerHolder = new CacheWorkerHolder(aBehavior);
   if (NS_WARN_IF(!workerHolder->HoldWorker(aWorkerPrivate, Terminating))) {
     return nullptr;
   }
@@ -30,6 +30,28 @@ CacheWorkerHolder::Create(WorkerPrivate* aWorkerPrivate)
   return workerHolder.forget();
 }
 
+// static
+already_AddRefed<CacheWorkerHolder>
+CacheWorkerHolder::PreferBehavior(CacheWorkerHolder* aCurrentHolder,
+                                  Behavior aBehavior)
+{
+  if (!aCurrentHolder) {
+    return nullptr;
+  }
+
+  RefPtr<CacheWorkerHolder> orig = aCurrentHolder;
+  if (orig->GetBehavior() == aBehavior) {
+    return orig.forget();
+  }
+
+  RefPtr<CacheWorkerHolder> replace = Create(orig->mWorkerPrivate, aBehavior);
+  if (!replace) {
+    return orig.forget();
+  }
+
+  return replace.forget();
+}
+
 void
 CacheWorkerHolder::AddActor(ActorChild* aActor)
 {
@@ -88,8 +110,9 @@ CacheWorkerHolder::Notify(Status aStatus)
   return true;
 }
 
-CacheWorkerHolder::CacheWorkerHolder()
-  : mNotified(false)
+CacheWorkerHolder::CacheWorkerHolder(Behavior aBehavior)
+  : WorkerHolder(aBehavior)
+  , mNotified(false)
 {
 }
 
diff --git a/dom/cache/CacheWorkerHolder.h b/dom/cache/CacheWorkerHolder.h
index 9eed7e2b6a..7e4c55f839 100644
--- a/dom/cache/CacheWorkerHolder.h
+++ b/dom/cache/CacheWorkerHolder.h
@@ -25,7 +25,11 @@ class CacheWorkerHolder final : public workers::WorkerHolder
 {
 public:
   static already_AddRefed<CacheWorkerHolder>
-  Create(workers::WorkerPrivate* aWorkerPrivate);
+  Create(workers::WorkerPrivate* aWorkerPrivate,
+         Behavior aBehavior);
+
+  static already_AddRefed<CacheWorkerHolder>
+  PreferBehavior(CacheWorkerHolder* aCurrentHolder, Behavior aBehavior);
 
   void AddActor(ActorChild* aActor);
   void RemoveActor(ActorChild* aActor);
@@ -36,7 +40,7 @@ public:
   virtual bool Notify(workers::Status aStatus) override;
 
 private:
-  CacheWorkerHolder();
+  explicit CacheWorkerHolder(Behavior aBehavior);
   ~CacheWorkerHolder();
 
   nsTArray<ActorChild*> mActorList;
diff --git a/dom/cache/TypeUtils.cpp b/dom/cache/TypeUtils.cpp
index f849f18874..1af5ee9458 100644
--- a/dom/cache/TypeUtils.cpp
+++ b/dom/cache/TypeUtils.cpp
@@ -79,7 +79,7 @@ ToHeadersEntryList(nsTArray<HeadersEntry>& aOut, InternalHeaders* aHeaders)
 } // namespace
 
 already_AddRefed<InternalRequest>
-TypeUtils::ToInternalRequest(const RequestOrUSVString& aIn,
+TypeUtils::ToInternalRequest(JSContext* aCx, const RequestOrUSVString& aIn,
                              BodyAction aBodyAction, ErrorResult& aRv)
 {
   if (aIn.IsRequest()) {
@@ -87,7 +87,7 @@ TypeUtils::ToInternalRequest(const RequestOrUSVString& aIn,
 
     // Check and set bodyUsed flag immediately because its on Request
     // instead of InternalRequest.
-    CheckAndSetBodyUsed(&request, aBodyAction, aRv);
+    CheckAndSetBodyUsed(aCx, &request, aBodyAction, aRv);
     if (aRv.Failed()) { return nullptr; }
 
     return request.GetInternalRequest();
@@ -97,7 +97,8 @@ TypeUtils::ToInternalRequest(const RequestOrUSVString& aIn,
 }
 
 already_AddRefed<InternalRequest>
-TypeUtils::ToInternalRequest(const OwningRequestOrUSVString& aIn,
+TypeUtils::ToInternalRequest(JSContext* aCx,
+                             const OwningRequestOrUSVString& aIn,
                              BodyAction aBodyAction, ErrorResult& aRv)
 {
 
@@ -106,7 +107,7 @@ TypeUtils::ToInternalRequest(const OwningRequestOrUSVString& aIn,
 
     // Check and set bodyUsed flag immediately because its on Request
     // instead of InternalRequest.
-    CheckAndSetBodyUsed(request, aBodyAction, aRv);
+    CheckAndSetBodyUsed(aCx, request, aBodyAction, aRv);
     if (aRv.Failed()) { return nullptr; }
 
     return request->GetInternalRequest();
@@ -204,7 +205,7 @@ TypeUtils::ToCacheResponseWithoutBody(CacheResponse& aOut,
 }
 
 void
-TypeUtils::ToCacheResponse(CacheResponse& aOut, Response& aIn,
+TypeUtils::ToCacheResponse(JSContext* aCx, CacheResponse& aOut, Response& aIn,
                            nsTArray<UniquePtr<AutoIPCStream>>& aStreamCleanupList,
                            ErrorResult& aRv)
 {
@@ -222,7 +223,10 @@ TypeUtils::ToCacheResponse(CacheResponse& aOut, Response& aIn,
   nsCOMPtr<nsIInputStream> stream;
   ir->GetUnfilteredBody(getter_AddRefs(stream));
   if (stream) {
-    aIn.SetBodyUsed();
+    aIn.SetBodyUsed(aCx, aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
   }
 
   SerializeCacheStream(stream, &aOut.body(), aStreamCleanupList, aRv);
@@ -426,8 +430,8 @@ TypeUtils::ProcessURL(nsACString& aUrl, bool* aSchemeValidOut,
 }
 
 void
-TypeUtils::CheckAndSetBodyUsed(Request* aRequest, BodyAction aBodyAction,
-                               ErrorResult& aRv)
+TypeUtils::CheckAndSetBodyUsed(JSContext* aCx, Request* aRequest,
+                               BodyAction aBodyAction, ErrorResult& aRv)
 {
   MOZ_DIAGNOSTIC_ASSERT(aRequest);
 
@@ -443,7 +447,10 @@ TypeUtils::CheckAndSetBodyUsed(Request* aRequest, BodyAction aBodyAction,
   nsCOMPtr<nsIInputStream> stream;
   aRequest->GetBody(getter_AddRefs(stream));
   if (stream) {
-    aRequest->SetBodyUsed();
+    aRequest->SetBodyUsed(aCx, aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
   }
 }
 
diff --git a/dom/cache/TypeUtils.h b/dom/cache/TypeUtils.h
index 274586e3f7..ff5816db3e 100644
--- a/dom/cache/TypeUtils.h
+++ b/dom/cache/TypeUtils.h
@@ -73,12 +73,12 @@ public:
   GetIPCManager() = 0;
 
   already_AddRefed<InternalRequest>
-  ToInternalRequest(const RequestOrUSVString& aIn, BodyAction aBodyAction,
-                    ErrorResult& aRv);
+  ToInternalRequest(JSContext* aCx, const RequestOrUSVString& aIn,
+                    BodyAction aBodyAction, ErrorResult& aRv);
 
   already_AddRefed<InternalRequest>
-  ToInternalRequest(const OwningRequestOrUSVString& aIn, BodyAction aBodyAction,
-                    ErrorResult& aRv);
+  ToInternalRequest(JSContext* aCx, const OwningRequestOrUSVString& aIn,
+                    BodyAction aBodyAction, ErrorResult& aRv);
 
   void
   ToCacheRequest(CacheRequest& aOut, InternalRequest* aIn,
@@ -91,7 +91,7 @@ public:
                              ErrorResult& aRv);
 
   void
-  ToCacheResponse(CacheResponse& aOut, Response& aIn,
+  ToCacheResponse(JSContext* aCx, CacheResponse& aOut, Response& aIn,
                   nsTArray<UniquePtr<mozilla::ipc::AutoIPCStream>>& aStreamCleanupList,
                   ErrorResult& aRv);
 
@@ -133,7 +133,7 @@ public:
 
 private:
   void
-  CheckAndSetBodyUsed(Request* aRequest, BodyAction aBodyAction,
+  CheckAndSetBodyUsed(JSContext* aCx, Request* aRequest, BodyAction aBodyAction,
                       ErrorResult& aRv);
 
   already_AddRefed<InternalRequest>
diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index ed263f75d2..1e7eab82b2 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -2974,8 +2974,8 @@ ValidateRect(double& aX, double& aY, double& aWidth, double& aHeight, bool aIsZe
   // The values of canvas API input are in double precision, but Moz2D APIs are
   // using float precision. Bypass canvas API calls when the input is out of
   // float precision to avoid precision problem
-  if (!std::isfinite((float)aX) | !std::isfinite((float)aY) |
-      !std::isfinite((float)aWidth) | !std::isfinite((float)aHeight)) {
+  if (!std::isfinite((float)aX) || !std::isfinite((float)aY) ||
+      !std::isfinite((float)aWidth) || !std::isfinite((float)aHeight)) {
     return false;
   }
 
@@ -5959,7 +5959,7 @@ void
 CanvasRenderingContext2D::PutImageData(ImageData& aImageData, double aDx,
                                        double aDy, ErrorResult& aError)
 {
-  RootedTypedArray<Uint8ClampedArray> arr(RootingCx());
+  RootedSpiderMonkeyInterface<Uint8ClampedArray> arr(RootingCx());
   DebugOnly<bool> inited = arr.Init(aImageData.GetDataObject());
   MOZ_ASSERT(inited);
 
@@ -5975,7 +5975,7 @@ CanvasRenderingContext2D::PutImageData(ImageData& aImageData, double aDx,
                                        double aDirtyHeight,
                                        ErrorResult& aError)
 {
-  RootedTypedArray<Uint8ClampedArray> arr(RootingCx());
+  RootedSpiderMonkeyInterface<Uint8ClampedArray> arr(RootingCx());
   DebugOnly<bool> inited = arr.Init(aImageData.GetDataObject());
   MOZ_ASSERT(inited);
 
diff --git a/dom/canvas/ImageBitmap.cpp b/dom/canvas/ImageBitmap.cpp
index 042c0fa11a..7aaf4e74d8 100644
--- a/dom/canvas/ImageBitmap.cpp
+++ b/dom/canvas/ImageBitmap.cpp
@@ -929,7 +929,7 @@ ImageBitmap::CreateInternal(nsIGlobalObject* aGlobal, ImageData& aImageData,
                             const Maybe<IntRect>& aCropRect, ErrorResult& aRv)
 {
   // Copy data into SourceSurface.
-  RootedTypedArray<Uint8ClampedArray> array(RootingCx());
+  RootedSpiderMonkeyInterface<Uint8ClampedArray> array(RootingCx());
   DebugOnly<bool> inited = array.Init(aImageData.GetDataObject());
   MOZ_ASSERT(inited);
 
diff --git a/dom/canvas/WebGLTextureUpload.cpp b/dom/canvas/WebGLTextureUpload.cpp
index ed199cfb43..661fb91ce2 100644
--- a/dom/canvas/WebGLTextureUpload.cpp
+++ b/dom/canvas/WebGLTextureUpload.cpp
@@ -475,7 +475,7 @@ WebGLTexture::TexImage(const char* funcName, TexImageTarget target, GLint level,
                        GLsizei depth, GLint border, const webgl::PackingInfo& pi,
                        const TexImageSource& src)
 {
-    dom::RootedTypedArray<dom::Uint8ClampedArray> scopedArr(dom::RootingCx());
+    dom::RootedSpiderMonkeyInterface<dom::Uint8ClampedArray> scopedArr(dom::RootingCx());
     const auto blob = ValidateTexOrSubImage(mContext, funcName, target, width, height,
                                             depth, border, pi, src, &scopedArr);
     if (!blob)
@@ -491,7 +491,7 @@ WebGLTexture::TexSubImage(const char* funcName, TexImageTarget target, GLint lev
                           const webgl::PackingInfo& pi, const TexImageSource& src)
 {
     const GLint border = 0;
-    dom::RootedTypedArray<dom::Uint8ClampedArray> scopedArr(dom::RootingCx());
+    dom::RootedSpiderMonkeyInterface<dom::Uint8ClampedArray> scopedArr(dom::RootingCx());
     const auto blob = ValidateTexOrSubImage(mContext, funcName, target, width, height,
                                             depth, border, pi, src, &scopedArr);
     if (!blob)
diff --git a/dom/crypto/WebCryptoTask.cpp b/dom/crypto/WebCryptoTask.cpp
index ed47325f8d..34a4c877d7 100644
--- a/dom/crypto/WebCryptoTask.cpp
+++ b/dom/crypto/WebCryptoTask.cpp
@@ -1366,7 +1366,7 @@ public:
     mDataIsJwk = false;
 
     // Try ArrayBuffer
-    RootedTypedArray<ArrayBuffer> ab(aCx);
+    RootedSpiderMonkeyInterface<ArrayBuffer> ab(aCx);
     if (ab.Init(aKeyData)) {
       if (!mKeyData.Assign(ab)) {
         mEarlyRv = NS_ERROR_DOM_OPERATION_ERR;
@@ -1375,7 +1375,7 @@ public:
     }
 
     // Try ArrayBufferView
-    RootedTypedArray<ArrayBufferView> abv(aCx);
+    RootedSpiderMonkeyInterface<ArrayBufferView> abv(aCx);
     if (abv.Init(aKeyData)) {
       if (!mKeyData.Assign(abv)) {
         mEarlyRv = NS_ERROR_DOM_OPERATION_ERR;
diff --git a/dom/fetch/BodyExtractor.cpp b/dom/fetch/BodyExtractor.cpp
new file mode 100644
index 0000000000..b840641214
--- /dev/null
+++ b/dom/fetch/BodyExtractor.cpp
@@ -0,0 +1,207 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BodyExtractor.h"
+#include "mozilla/dom/EncodingUtils.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FormData.h"
+#include "mozilla/dom/TypedArray.h"
+#include "mozilla/dom/URLSearchParams.h"
+#include "mozilla/dom/XMLHttpRequest.h"
+#include "nsContentUtils.h"
+#include "nsIDOMDocument.h"
+#include "nsIDOMSerializer.h"
+#include "nsIGlobalObject.h"
+#include "nsIInputStream.h"
+#include "nsIOutputStream.h"
+#include "nsIStorageStream.h"
+#include "nsStringStream.h"
+#include "nsIUnicodeEncoder.h"
+
+namespace mozilla {
+namespace dom {
+
+static nsresult
+GetBufferDataAsStream(const uint8_t* aData, uint32_t aDataLength,
+                      nsIInputStream** aResult, uint64_t* aContentLength,
+                      nsACString& aContentType, nsACString& aCharset)
+{
+  aContentType.SetIsVoid(true);
+  aCharset.Truncate();
+
+  *aContentLength = aDataLength;
+  const char* data = reinterpret_cast<const char*>(aData);
+
+  nsCOMPtr<nsIInputStream> stream;
+  nsresult rv = NS_NewByteInputStream(getter_AddRefs(stream), data, aDataLength,
+                                      NS_ASSIGNMENT_COPY);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  stream.forget(aResult);
+
+  return NS_OK;
+}
+
+template<> nsresult
+BodyExtractor<const ArrayBuffer>::GetAsStream(nsIInputStream** aResult,
+                                              uint64_t* aContentLength,
+                                              nsACString& aContentTypeWithCharset,
+                                              nsACString& aCharset) const
+{
+  mBody->ComputeLengthAndData();
+  return GetBufferDataAsStream(mBody->Data(), mBody->Length(),
+                               aResult, aContentLength, aContentTypeWithCharset,
+                               aCharset);
+}
+
+template<> nsresult
+BodyExtractor<const ArrayBufferView>::GetAsStream(nsIInputStream** aResult,
+                                                  uint64_t* aContentLength,
+                                                  nsACString& aContentTypeWithCharset,
+                                                  nsACString& aCharset) const
+{
+  mBody->ComputeLengthAndData();
+  return GetBufferDataAsStream(mBody->Data(), mBody->Length(),
+                               aResult, aContentLength, aContentTypeWithCharset,
+                               aCharset);
+}
+
+template<> nsresult
+BodyExtractor<nsIDocument>::GetAsStream(nsIInputStream** aResult,
+                                        uint64_t* aContentLength,
+                                        nsACString& aContentTypeWithCharset,
+                                        nsACString& aCharset) const
+{
+  nsCOMPtr<nsIDOMDocument> domdoc(do_QueryInterface(mBody));
+  NS_ENSURE_STATE(domdoc);
+  aCharset.AssignLiteral("UTF-8");
+
+  nsresult rv;
+  nsCOMPtr<nsIStorageStream> storStream;
+  rv = NS_NewStorageStream(4096, UINT32_MAX, getter_AddRefs(storStream));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIOutputStream> output;
+  rv = storStream->GetOutputStream(0, getter_AddRefs(output));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (mBody->IsHTMLDocument()) {
+    aContentTypeWithCharset.AssignLiteral("text/html;charset=UTF-8");
+
+    nsString serialized;
+    if (!nsContentUtils::SerializeNodeToMarkup(mBody, true, serialized)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    nsAutoCString utf8Serialized;
+    if (!AppendUTF16toUTF8(serialized, utf8Serialized, fallible)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    uint32_t written;
+    rv = output->Write(utf8Serialized.get(), utf8Serialized.Length(), &written);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MOZ_ASSERT(written == utf8Serialized.Length());
+  } else {
+    aContentTypeWithCharset.AssignLiteral("application/xml;charset=UTF-8");
+
+    nsCOMPtr<nsIDOMSerializer> serializer =
+      do_CreateInstance(NS_XMLSERIALIZER_CONTRACTID, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Make sure to use the encoding we'll send
+    rv = serializer->SerializeToStream(domdoc, output, aCharset);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  output->Close();
+
+  uint32_t length;
+  rv = storStream->GetLength(&length);
+  NS_ENSURE_SUCCESS(rv, rv);
+  *aContentLength = length;
+
+  rv = storStream->NewInputStream(0, aResult);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+template<> nsresult
+BodyExtractor<const nsAString>::GetAsStream(nsIInputStream** aResult,
+                                            uint64_t* aContentLength,
+                                            nsACString& aContentTypeWithCharset,
+                                            nsACString& aCharset) const
+{
+  nsCOMPtr<nsIUnicodeEncoder> encoder =
+    EncodingUtils::EncoderForEncoding("UTF-8");
+  if (!encoder) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  int32_t destBufferLen;
+  nsresult rv = encoder->GetMaxLength(mBody->BeginReading(), mBody->Length(),
+                                      &destBufferLen);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCString encoded;
+  if (!encoded.SetCapacity(destBufferLen, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  char* destBuffer = encoded.BeginWriting();
+  int32_t srcLen = (int32_t) mBody->Length();
+  int32_t outLen = destBufferLen;
+  rv = encoder->Convert(mBody->BeginReading(), &srcLen, destBuffer, &outLen);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  MOZ_ASSERT(outLen <= destBufferLen);
+  encoded.SetLength(outLen);
+
+  rv = NS_NewCStringInputStream(aResult, encoded);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  *aContentLength = outLen;
+  aContentTypeWithCharset.AssignLiteral("text/plain;charset=UTF-8");
+  aCharset.AssignLiteral("UTF-8");
+  return NS_OK;
+}
+
+template<> nsresult
+BodyExtractor<nsIInputStream>::GetAsStream(nsIInputStream** aResult,
+                                           uint64_t* aContentLength,
+                                           nsACString& aContentTypeWithCharset,
+                                           nsACString& aCharset) const
+{
+  aContentTypeWithCharset.AssignLiteral("text/plain");
+  aCharset.Truncate();
+
+  nsresult rv = mBody->Available(aContentLength);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIInputStream> stream(mBody);
+  stream.forget(aResult);
+  return NS_OK;
+}
+
+template<> nsresult
+BodyExtractor<nsIXHRSendable>::GetAsStream(nsIInputStream** aResult,
+                                           uint64_t* aContentLength,
+                                           nsACString& aContentTypeWithCharset,
+                                           nsACString& aCharset) const
+{
+  return mBody->GetSendInfo(aResult, aContentLength, aContentTypeWithCharset,
+                            aCharset);
+}
+
+} // dom namespace
+} // mozilla namespace
diff --git a/dom/fetch/BodyExtractor.h b/dom/fetch/BodyExtractor.h
new file mode 100644
index 0000000000..73dfef6aff
--- /dev/null
+++ b/dom/fetch/BodyExtractor.h
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BodyExtractor_h
+#define mozilla_dom_BodyExtractor_h
+
+#include "jsapi.h"
+#include "nsString.h"
+
+class nsIInputStream;
+class nsIGlobalObject;
+
+namespace mozilla {
+namespace dom {
+
+class BodyExtractorBase
+{
+public:
+  virtual nsresult GetAsStream(nsIInputStream** aResult,
+                               uint64_t* aContentLength,
+                               nsACString& aContentTypeWithCharset,
+                               nsACString& aCharset) const = 0;
+};
+
+// The implementation versions of this template are:
+// ArrayBuffer, ArrayBufferView, nsIXHRSendable (Blob, FormData,
+// URLSearchParams), nsAString, nsIDocument, nsIInputStream.
+template<typename Type>
+class BodyExtractor final : public BodyExtractorBase
+{
+  Type* mBody;
+public:
+  explicit BodyExtractor(Type* aBody) : mBody(aBody)
+  {}
+
+  nsresult GetAsStream(nsIInputStream** aResult,
+                       uint64_t* aContentLength,
+                       nsACString& aContentTypeWithCharset,
+                       nsACString& aCharset) const override;
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_BodyExtractor_h
diff --git a/dom/fetch/Fetch.cpp b/dom/fetch/Fetch.cpp
index 6a6b4faaf8..a9d8514765 100644
--- a/dom/fetch/Fetch.cpp
+++ b/dom/fetch/Fetch.cpp
@@ -5,13 +5,13 @@
 
 #include "Fetch.h"
 #include "FetchConsumer.h"
+#include "FetchStream.h"
 
 #include "nsIDocument.h"
 #include "nsIGlobalObject.h"
 #include "nsIStreamLoader.h"
 #include "nsIThreadRetargetableRequest.h"
 #include "nsIUnicodeDecoder.h"
-#include "nsIUnicodeEncoder.h"
 
 #include "nsDOMString.h"
 #include "nsNetUtil.h"
@@ -22,7 +22,7 @@
 
 #include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BodyUtil.h"
-#include "mozilla/dom/EncodingUtils.h"
+#include "mozilla/dom/DOMError.h"
 #include "mozilla/dom/Exceptions.h"
 #include "mozilla/dom/FetchDriver.h"
 #include "mozilla/dom/File.h"
@@ -35,8 +35,10 @@
 #include "mozilla/dom/Response.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/dom/URLSearchParams.h"
+#include "mozilla/dom/WorkerPrivate.h"
 #include "mozilla/dom/workers/ServiceWorkerManager.h"
 
+#include "BodyExtractor.h"
 #include "FetchObserver.h"
 #include "InternalRequest.h"
 #include "InternalResponse.h"
@@ -722,154 +724,95 @@ WorkerFetchResolver::FlushConsoleReport()
   mReporter->FlushConsoleReports(worker->GetDocument());
 }
 
-namespace {
-
-nsresult
-ExtractFromArrayBuffer(const ArrayBuffer& aBuffer,
-                       nsIInputStream** aStream,
-                       uint64_t& aContentLength)
-{
-  aBuffer.ComputeLengthAndData();
-  aContentLength = aBuffer.Length();
-  //XXXnsm reinterpret_cast<> is used in DOMParser, should be ok.
-  return NS_NewByteInputStream(aStream,
-                               reinterpret_cast<char*>(aBuffer.Data()),
-                               aBuffer.Length(), NS_ASSIGNMENT_COPY);
-}
-
 nsresult
-ExtractFromArrayBufferView(const ArrayBufferView& aBuffer,
-                           nsIInputStream** aStream,
-                           uint64_t& aContentLength)
+ExtractByteStreamFromBody(const fetch::OwningBodyInit& aBodyInit,
+                          nsIInputStream** aStream,
+                          nsCString& aContentTypeWithCharset,
+                          uint64_t& aContentLength)
 {
-  aBuffer.ComputeLengthAndData();
-  aContentLength = aBuffer.Length();
-  //XXXnsm reinterpret_cast<> is used in DOMParser, should be ok.
-  return NS_NewByteInputStream(aStream,
-                               reinterpret_cast<char*>(aBuffer.Data()),
-                               aBuffer.Length(), NS_ASSIGNMENT_COPY);
-}
+  MOZ_ASSERT(aStream);
+  nsAutoCString charset;
+  aContentTypeWithCharset.SetIsVoid(true);
 
-nsresult
-ExtractFromBlob(const Blob& aBlob,
-                nsIInputStream** aStream,
-                nsCString& aContentType,
-                uint64_t& aContentLength)
-{
-  RefPtr<BlobImpl> impl = aBlob.Impl();
-  ErrorResult rv;
-  aContentLength = impl->GetSize(rv);
-  if (NS_WARN_IF(rv.Failed())) {
-    return rv.StealNSResult();
+  if (aBodyInit.IsArrayBuffer()) {
+    BodyExtractor<const ArrayBuffer> body(&aBodyInit.GetAsArrayBuffer());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
-
-  impl->GetInternalStream(aStream, rv);
-  if (NS_WARN_IF(rv.Failed())) {
-    return rv.StealNSResult();
+  if (aBodyInit.IsArrayBufferView()) {
+    BodyExtractor<const ArrayBufferView> body(&aBodyInit.GetAsArrayBufferView());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
-
-  nsAutoString type;
-  impl->GetType(type);
-  aContentType = NS_ConvertUTF16toUTF8(type);
-  return NS_OK;
-}
-
-nsresult
-ExtractFromFormData(FormData& aFormData,
-                    nsIInputStream** aStream,
-                    nsCString& aContentType,
-                    uint64_t& aContentLength)
-{
-  nsAutoCString unusedCharset;
-  return aFormData.GetSendInfo(aStream, &aContentLength,
-                               aContentType, unusedCharset);
-}
-
-nsresult
-ExtractFromUSVString(const nsString& aStr,
-                     nsIInputStream** aStream,
-                     nsCString& aContentType,
-                     uint64_t& aContentLength)
-{
-  nsCOMPtr<nsIUnicodeEncoder> encoder = EncodingUtils::EncoderForEncoding("UTF-8");
-  if (!encoder) {
-    return NS_ERROR_OUT_OF_MEMORY;
+  if (aBodyInit.IsBlob()) {
+    Blob& blob = aBodyInit.GetAsBlob();
+    BodyExtractor<nsIXHRSendable> body(&blob);
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
-
-  int32_t destBufferLen;
-  nsresult rv = encoder->GetMaxLength(aStr.get(), aStr.Length(), &destBufferLen);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
+  if (aBodyInit.IsFormData()) {
+    FormData& formData = aBodyInit.GetAsFormData();
+    BodyExtractor<nsIXHRSendable> body(&formData);
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
-
-  nsCString encoded;
-  if (!encoded.SetCapacity(destBufferLen, fallible)) {
-    return NS_ERROR_OUT_OF_MEMORY;
+  if (aBodyInit.IsUSVString()) {
+    BodyExtractor<const nsAString> body(&aBodyInit.GetAsUSVString());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
-
-  char* destBuffer = encoded.BeginWriting();
-  int32_t srcLen = (int32_t) aStr.Length();
-  int32_t outLen = destBufferLen;
-  rv = encoder->Convert(aStr.get(), &srcLen, destBuffer, &outLen);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return rv;
+  if (aBodyInit.IsURLSearchParams()) {
+    URLSearchParams& usp = aBodyInit.GetAsURLSearchParams();
+    BodyExtractor<nsIXHRSendable> body(&usp);
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
 
-  MOZ_ASSERT(outLen <= destBufferLen);
-  encoded.SetLength(outLen);
-
-  aContentType = NS_LITERAL_CSTRING("text/plain;charset=UTF-8");
-  aContentLength = outLen;
-
-  return NS_NewCStringInputStream(aStream, encoded);
-}
-
-nsresult
-ExtractFromURLSearchParams(const URLSearchParams& aParams,
-                           nsIInputStream** aStream,
-                           nsCString& aContentType,
-                           uint64_t& aContentLength)
-{
-  nsAutoString serialized;
-  aParams.Stringify(serialized);
-  aContentType = NS_LITERAL_CSTRING("application/x-www-form-urlencoded;charset=UTF-8");
-  aContentLength = serialized.Length();
-  return NS_NewCStringInputStream(aStream, NS_ConvertUTF16toUTF8(serialized));
+  NS_NOTREACHED("Should never reach here");
+  return NS_ERROR_FAILURE;
 }
-} // namespace
 
 nsresult
-ExtractByteStreamFromBody(const OwningArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams& aBodyInit,
+ExtractByteStreamFromBody(const fetch::BodyInit& aBodyInit,
                           nsIInputStream** aStream,
-                          nsCString& aContentType,
+                          nsCString& aContentTypeWithCharset,
                           uint64_t& aContentLength)
 {
   MOZ_ASSERT(aStream);
+  MOZ_ASSERT(!*aStream);
+
+  nsAutoCString charset;
+  aContentTypeWithCharset.SetIsVoid(true);
 
   if (aBodyInit.IsArrayBuffer()) {
-    const ArrayBuffer& buf = aBodyInit.GetAsArrayBuffer();
-    return ExtractFromArrayBuffer(buf, aStream, aContentLength);
+    BodyExtractor<const ArrayBuffer> body(&aBodyInit.GetAsArrayBuffer());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
   if (aBodyInit.IsArrayBufferView()) {
-    const ArrayBufferView& buf = aBodyInit.GetAsArrayBufferView();
-    return ExtractFromArrayBufferView(buf, aStream, aContentLength);
+    BodyExtractor<const ArrayBufferView> body(&aBodyInit.GetAsArrayBufferView());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
   if (aBodyInit.IsBlob()) {
-    const Blob& blob = aBodyInit.GetAsBlob();
-    return ExtractFromBlob(blob, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsBlob());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
   if (aBodyInit.IsFormData()) {
-    FormData& form = aBodyInit.GetAsFormData();
-    return ExtractFromFormData(form, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsFormData());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
   if (aBodyInit.IsUSVString()) {
-    nsAutoString str;
-    str.Assign(aBodyInit.GetAsUSVString());
-    return ExtractFromUSVString(str, aStream, aContentType, aContentLength);
+    BodyExtractor<const nsAString> body(&aBodyInit.GetAsUSVString());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
   if (aBodyInit.IsURLSearchParams()) {
-    URLSearchParams& params = aBodyInit.GetAsURLSearchParams();
-    return ExtractFromURLSearchParams(params, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsURLSearchParams());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
 
   NS_NOTREACHED("Should never reach here");
@@ -877,69 +820,181 @@ ExtractByteStreamFromBody(const OwningArrayBufferOrArrayBufferViewOrBlobOrFormDa
 }
 
 nsresult
-ExtractByteStreamFromBody(const ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams& aBodyInit,
+ExtractByteStreamFromBody(const fetch::ResponseBodyInit& aBodyInit,
                           nsIInputStream** aStream,
-                          nsCString& aContentType,
+                          nsCString& aContentTypeWithCharset,
                           uint64_t& aContentLength)
 {
   MOZ_ASSERT(aStream);
   MOZ_ASSERT(!*aStream);
 
+  // ReadableStreams should be handled by
+  // BodyExtractorReadableStream::GetAsStream.
+  MOZ_ASSERT(!aBodyInit.IsReadableStream());
+
+  nsAutoCString charset;
+  aContentTypeWithCharset.SetIsVoid(true);
+
   if (aBodyInit.IsArrayBuffer()) {
-    const ArrayBuffer& buf = aBodyInit.GetAsArrayBuffer();
-    return ExtractFromArrayBuffer(buf, aStream, aContentLength);
+    BodyExtractor<const ArrayBuffer> body(&aBodyInit.GetAsArrayBuffer());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
+
   if (aBodyInit.IsArrayBufferView()) {
-    const ArrayBufferView& buf = aBodyInit.GetAsArrayBufferView();
-    return ExtractFromArrayBufferView(buf, aStream, aContentLength);
+    BodyExtractor<const ArrayBufferView> body(&aBodyInit.GetAsArrayBufferView());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
+
   if (aBodyInit.IsBlob()) {
-    const Blob& blob = aBodyInit.GetAsBlob();
-    return ExtractFromBlob(blob, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsBlob());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
+
   if (aBodyInit.IsFormData()) {
-    FormData& form = aBodyInit.GetAsFormData();
-    return ExtractFromFormData(form, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsFormData());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
+
   if (aBodyInit.IsUSVString()) {
-    nsAutoString str;
-    str.Assign(aBodyInit.GetAsUSVString());
-    return ExtractFromUSVString(str, aStream, aContentType, aContentLength);
+    BodyExtractor<const nsAString> body(&aBodyInit.GetAsUSVString());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
+
   if (aBodyInit.IsURLSearchParams()) {
-    URLSearchParams& params = aBodyInit.GetAsURLSearchParams();
-    return ExtractFromURLSearchParams(params, aStream, aContentType, aContentLength);
+    BodyExtractor<nsIXHRSendable> body(&aBodyInit.GetAsURLSearchParams());
+    return body.GetAsStream(aStream, &aContentLength, aContentTypeWithCharset,
+                            charset);
   }
 
   NS_NOTREACHED("Should never reach here");
   return NS_ERROR_FAILURE;
 }
 
+
 template <class Derived>
-FetchBody<Derived>::FetchBody()
+FetchBody<Derived>::FetchBody(nsIGlobalObject* aOwner)
   : mWorkerPrivate(nullptr)
+  , mOwner(aOwner)
+  , mReadableStreamBody(nullptr)
+  , mReadableStreamReader(nullptr)
   , mBodyUsed(false)
 {
+  MOZ_ASSERT(aOwner);
+
   if (!NS_IsMainThread()) {
     mWorkerPrivate = GetCurrentThreadWorkerPrivate();
     MOZ_ASSERT(mWorkerPrivate);
+  } else {
+    mWorkerPrivate = nullptr;
   }
 }
 
 template
-FetchBody<Request>::FetchBody();
+FetchBody<Request>::FetchBody(nsIGlobalObject* aOwner);
 
 template
-FetchBody<Response>::FetchBody();
+FetchBody<Response>::FetchBody(nsIGlobalObject* aOwner);
 
 template <class Derived>
 FetchBody<Derived>::~FetchBody()
 {
 }
 
+template
+FetchBody<Request>::~FetchBody();
+
+template
+FetchBody<Response>::~FetchBody();
+
+template <class Derived>
+bool
+FetchBody<Derived>::BodyUsed() const
+{
+  if (mBodyUsed) {
+    return true;
+  }
+
+  // If this object is disturbed or locked, return false.
+  if (mReadableStreamBody) {
+    AutoJSAPI jsapi;
+    if (!jsapi.Init(mOwner)) {
+      return true;
+    }
+
+    JSContext* cx = jsapi.cx();
+
+    JS::Rooted<JSObject*> body(cx, mReadableStreamBody);
+    if (JS::ReadableStreamIsDisturbed(body) ||
+        JS::ReadableStreamIsLocked(body) ||
+        !JS::ReadableStreamIsReadable(body)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+template
+bool
+FetchBody<Request>::BodyUsed() const;
+
+template
+bool
+FetchBody<Response>::BodyUsed() const;
+
+template <class Derived>
+void
+FetchBody<Derived>::SetBodyUsed(JSContext* aCx, ErrorResult& aRv)
+{
+  MOZ_ASSERT(aCx);
+
+  if (mBodyUsed) {
+    return;
+  }
+
+  mBodyUsed = true;
+
+  // If we already have a ReadableStreamBody and it has been created by DOM, we
+  // have to lock it now because it can have been shared with other objects.
+  if (mReadableStreamBody) {
+    JS::Rooted<JSObject*> readableStreamObj(aCx, mReadableStreamBody);
+    if (JS::ReadableStreamGetMode(readableStreamObj) ==
+          JS::ReadableStreamMode::ExternalSource) {
+      LockStream(aCx, readableStreamObj, aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return;
+      }
+    } else {
+      // If this is not a native ReadableStream, let's activate the
+      // FetchStreamReader.
+      MOZ_ASSERT(mFetchStreamReader);
+      JS::Rooted<JSObject*> reader(aCx);
+      mFetchStreamReader->StartConsuming(aCx, readableStreamObj, &reader, aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return;
+      }
+
+      mReadableStreamReader = reader;
+    }
+  }
+}
+
+template
+void
+FetchBody<Request>::SetBodyUsed(JSContext* aCx, ErrorResult& aRv);
+
+template
+void
+FetchBody<Response>::SetBodyUsed(JSContext* aCx, ErrorResult& aRv);
+
 template <class Derived>
 already_AddRefed<Promise>
-FetchBody<Derived>::ConsumeBody(FetchConsumeType aType, ErrorResult& aRv)
+FetchBody<Derived>::ConsumeBody(JSContext* aCx, FetchConsumeType aType, ErrorResult& aRv)
 {
   RefPtr<AbortSignal> signal = DerivedClass()->GetSignal();
   if (signal && signal->Aborted()) {
@@ -952,11 +1007,15 @@ FetchBody<Derived>::ConsumeBody(FetchConsumeType aType, ErrorResult& aRv)
     return nullptr;
   }
 
-  SetBodyUsed();
+  SetBodyUsed(aCx, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = DerivedClass()->GetParentObject();
 
   RefPtr<Promise> promise =
-    FetchBodyConsumer<Derived>::Create(DerivedClass()->GetParentObject(),
-                                       this, signal, aType, aRv);
+    FetchBodyConsumer<Derived>::Create(global, this, signal, aType, aRv);
   if (NS_WARN_IF(aRv.Failed())) {
     return nullptr;
   }
@@ -966,11 +1025,11 @@ FetchBody<Derived>::ConsumeBody(FetchConsumeType aType, ErrorResult& aRv)
 
 template
 already_AddRefed<Promise>
-FetchBody<Request>::ConsumeBody(FetchConsumeType aType, ErrorResult& aRv);
+FetchBody<Request>::ConsumeBody(JSContext* aCx, FetchConsumeType aType, ErrorResult& aRv);
 
 template
 already_AddRefed<Promise>
-FetchBody<Response>::ConsumeBody(FetchConsumeType aType, ErrorResult& aRv);
+FetchBody<Response>::ConsumeBody(JSContext* aCx, FetchConsumeType aType, ErrorResult& aRv);
 
 template <class Derived>
 void
@@ -1000,5 +1059,170 @@ template
 void
 FetchBody<Response>::SetMimeType();
 
+template <class Derived>
+void
+FetchBody<Derived>::SetReadableStreamBody(JSObject* aBody)
+{
+  MOZ_ASSERT(!mReadableStreamBody);
+  MOZ_ASSERT(aBody);
+  mReadableStreamBody = aBody;
+}
+
+template
+void
+FetchBody<Request>::SetReadableStreamBody(JSObject* aBody);
+
+template
+void
+FetchBody<Response>::SetReadableStreamBody(JSObject* aBody);
+
+template <class Derived>
+void
+FetchBody<Derived>::GetBody(JSContext* aCx,
+                            JS::MutableHandle<JSObject*> aBodyOut,
+                            ErrorResult& aRv)
+{
+  if (mReadableStreamBody) {
+    aBodyOut.set(mReadableStreamBody);
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  DerivedClass()->GetBody(getter_AddRefs(inputStream));
+
+  if (!inputStream) {
+    aBodyOut.set(nullptr);
+    return;
+  }
+
+  JS::Rooted<JSObject*> body(aCx);
+  FetchStream::Create(aCx, this, DerivedClass()->GetParentObject(),
+                      inputStream, &body, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  MOZ_ASSERT(body);
+
+  // If the body has been already consumed, we lock the stream.
+  if (BodyUsed()) {
+    LockStream(aCx, body, aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  mReadableStreamBody = body;
+  aBodyOut.set(mReadableStreamBody);
+}
+
+template
+void
+FetchBody<Request>::GetBody(JSContext* aCx,
+                            JS::MutableHandle<JSObject*> aMessage,
+                            ErrorResult& aRv);
+
+template
+void
+FetchBody<Response>::GetBody(JSContext* aCx,
+                             JS::MutableHandle<JSObject*> aMessage,
+                             ErrorResult& aRv);
+
+template <class Derived>
+void
+FetchBody<Derived>::LockStream(JSContext* aCx,
+                               JS::HandleObject aStream,
+                               ErrorResult& aRv)
+{
+  MOZ_ASSERT(JS::ReadableStreamGetMode(aStream) ==
+               JS::ReadableStreamMode::ExternalSource);
+
+  // This is native stream, creating a reader will not execute any JS code.
+  JS::Rooted<JSObject*> reader(aCx,
+                               JS::ReadableStreamGetReader(aCx, aStream,
+                                                           JS::ReadableStreamReaderMode::Default));
+  if (!reader) {
+    aRv.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  mReadableStreamReader = reader;
+}
+
+template
+void
+FetchBody<Request>::LockStream(JSContext* aCx,
+                               JS::HandleObject aStream,
+                               ErrorResult& aRv);
+
+template
+void
+FetchBody<Response>::LockStream(JSContext* aCx,
+                                JS::HandleObject aStream,
+                                ErrorResult& aRv);
+
+template <class Derived>
+void
+FetchBody<Derived>::MaybeTeeReadableStreamBody(JSContext* aCx,
+                                               JS::MutableHandle<JSObject*> aBodyOut,
+                                               FetchStreamReader** aStreamReader,
+                                               nsIInputStream** aInputStream,
+                                               ErrorResult& aRv)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aStreamReader);
+  MOZ_DIAGNOSTIC_ASSERT(aInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(!BodyUsed());
+
+  aBodyOut.set(nullptr);
+  *aStreamReader = nullptr;
+  *aInputStream = nullptr;
+
+  if (!mReadableStreamBody) {
+    return;
+  }
+
+  JS::Rooted<JSObject*> stream(aCx, mReadableStreamBody);
+
+  // If this is a ReadableStream with an external source, this has been
+  // generated by a Fetch. In this case, Fetch will be able to recreate it
+  // again when GetBody() is called.
+  if (JS::ReadableStreamGetMode(stream) == JS::ReadableStreamMode::ExternalSource) {
+    aBodyOut.set(nullptr);
+    return;
+  }
+
+  JS::Rooted<JSObject*> branch1(aCx);
+  JS::Rooted<JSObject*> branch2(aCx);
+
+  if (!JS::ReadableStreamTee(aCx, stream, &branch1, &branch2)) {
+    aRv.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  mReadableStreamBody = branch1;
+  aBodyOut.set(branch2);
+
+  aRv = FetchStreamReader::Create(aCx, mOwner, aStreamReader, aInputStream);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+}
+
+template
+void
+FetchBody<Request>::MaybeTeeReadableStreamBody(JSContext* aCx,
+                                               JS::MutableHandle<JSObject*> aMessage,
+                                               FetchStreamReader** aStreamReader,
+                                               nsIInputStream** aInputStream,
+                                               ErrorResult& aRv);
+
+template
+void
+FetchBody<Response>::MaybeTeeReadableStreamBody(JSContext* aCx,
+                                                JS::MutableHandle<JSObject*> aMessage,
+                                                FetchStreamReader** aStreamReader,
+                                                nsIInputStream** aInputStream,
+                                                ErrorResult& aRv);
+
 } // namespace dom
 } // namespace mozilla
diff --git a/dom/fetch/Fetch.h b/dom/fetch/Fetch.h
index 73d5c15199..19b579cb6c 100644
--- a/dom/fetch/Fetch.h
+++ b/dom/fetch/Fetch.h
@@ -1,207 +1,312 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_dom_Fetch_h
-#define mozilla_dom_Fetch_h
-
-#include "nsAutoPtr.h"
-#include "nsIStreamLoader.h"
-
-#include "nsCOMPtr.h"
-#include "nsError.h"
-#include "nsProxyRelease.h"
-#include "nsString.h"
-
-#include "mozilla/DebugOnly.h"
-#include "mozilla/ErrorResult.h"
-#include "mozilla/dom/Promise.h"
-#include "mozilla/dom/RequestBinding.h"
-
-class nsIGlobalObject;
-
-namespace mozilla {
-namespace dom {
-
-class ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams;
-class BlobImpl;
-class InternalRequest;
-class OwningArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams;
-class RequestOrUSVString;
-
-namespace workers {
-class WorkerPrivate;
-} // namespace workers
-
-already_AddRefed<Promise>
-FetchRequest(nsIGlobalObject* aGlobal, const RequestOrUSVString& aInput,
-             const RequestInit& aInit, ErrorResult& aRv);
-
-nsresult
-UpdateRequestReferrer(nsIGlobalObject* aGlobal, InternalRequest* aRequest);
-
-/*
- * Creates an nsIInputStream based on the fetch specifications 'extract a byte
- * stream algorithm' - http://fetch.spec.whatwg.org/#concept-bodyinit-extract.
- * Stores content type in out param aContentType.
- */
-nsresult
-ExtractByteStreamFromBody(const OwningArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams& aBodyInit,
-                          nsIInputStream** aStream,
-                          nsCString& aContentType,
-                          uint64_t& aContentLength);
-
-/*
- * Non-owning version.
- */
-nsresult
-ExtractByteStreamFromBody(const ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams& aBodyInit,
-                          nsIInputStream** aStream,
-                          nsCString& aContentType,
-                          uint64_t& aContentLength);
-
-template <class Derived> class FetchBodyConsumer;
-
-enum FetchConsumeType
-{
-  CONSUME_ARRAYBUFFER,
-  CONSUME_BLOB,
-  CONSUME_FORMDATA,
-  CONSUME_JSON,
-  CONSUME_TEXT,
-};
-
-/*
- * FetchBody's body consumption uses nsIInputStreamPump to read from the
- * underlying stream to a block of memory, which is then adopted by
- * ContinueConsumeBody() and converted to the right type based on the JS
- * function called.
- *
- * Use of the nsIInputStreamPump complicates things on the worker thread.
- * The solution used here is similar to WebSockets.
- * The difference is that we are only interested in completion and not data
- * events, and nsIInputStreamPump can only deliver completion on the main thread.
- *
- * Before starting the pump on the main thread, we addref the FetchBody to keep
- * it alive. Then we add a feature, to track the status of the worker.
- *
- * ContinueConsumeBody() is the function that cleans things up in both success
- * and error conditions and so all callers call it with the appropriate status.
- *
- * Once the read is initiated on the main thread there are two possibilities.
- *
- * 1) Pump finishes before worker has finished Running.
- *    In this case we adopt the data and dispatch a runnable to the worker,
- *    which derefs FetchBody and removes the feature and resolves the Promise.
- *
- * 2) Pump still working while worker has stopped Running.
- *    The feature is Notify()ed and ContinueConsumeBody() is called with
- *    NS_BINDING_ABORTED. We first Cancel() the pump using a sync runnable to
- *    ensure that mFetchBody remains alive (since mConsumeBodyPump is strongly
- *    held by it) until pump->Cancel() is called. OnStreamComplete() will not
- *    do anything if the error code is NS_BINDING_ABORTED, so we don't have to
- *    worry about keeping anything alive.
- *
- * The pump is always released on the main thread.
- */
-template <class Derived>
-class FetchBody
-{
-public:
-  friend class FetchBodyConsumer<Derived>;
-
-  NS_IMETHOD_(MozExternalRefCountType) AddRef(void) = 0;
-  NS_IMETHOD_(MozExternalRefCountType) Release(void) = 0;
-
-  bool
-  BodyUsed() const { return mBodyUsed; }
-
-  already_AddRefed<Promise>
-  ArrayBuffer(ErrorResult& aRv)
-  {
-    return ConsumeBody(CONSUME_ARRAYBUFFER, aRv);
-  }
-
-  already_AddRefed<Promise>
-  Blob(ErrorResult& aRv)
-  {
-    return ConsumeBody(CONSUME_BLOB, aRv);
-  }
-
-  already_AddRefed<Promise>
-  FormData(ErrorResult& aRv)
-  {
-    return ConsumeBody(CONSUME_FORMDATA, aRv);
-  }
-
-  already_AddRefed<Promise>
-  Json(ErrorResult& aRv)
-  {
-    return ConsumeBody(CONSUME_JSON, aRv);
-  }
-
-  already_AddRefed<Promise>
-  Text(ErrorResult& aRv)
-  {
-    return ConsumeBody(CONSUME_TEXT, aRv);
-  }
-
-  // Utility public methods accessed by various runnables.
-
-  void
-  SetBodyUsed()
-  {
-    mBodyUsed = true;
-  }
-
-  const nsCString&
-  MimeType() const
-  {
-    return mMimeType;
-  }
-
-  virtual AbortSignal*
-  GetSignal() const = 0;
-
-protected:
-  FetchBody();
-
-  // Always set whenever the FetchBody is created on the worker thread.
-  workers::WorkerPrivate* mWorkerPrivate;
-
-  virtual ~FetchBody();
-
-  void
-  SetMimeType();
-private:
-  Derived*
-  DerivedClass() const
-  {
-    return static_cast<Derived*>(const_cast<FetchBody*>(this));
-  }
-
-  already_AddRefed<Promise>
-  ConsumeBody(FetchConsumeType aType, ErrorResult& aRv);
-
-  bool
-  IsOnTargetThread()
-  {
-    return NS_IsMainThread() == !mWorkerPrivate;
-  }
-
-  void
-  AssertIsOnTargetThread()
-  {
-    MOZ_ASSERT(IsOnTargetThread());
-  }
-
-  // Only ever set once, always on target thread.
-  bool mBodyUsed;
-  nsCString mMimeType;
-};
-
-} // namespace dom
-} // namespace mozilla
-
-#endif // mozilla_dom_Fetch_h
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this

+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

+

+#ifndef mozilla_dom_Fetch_h

+#define mozilla_dom_Fetch_h

+

+#include "nsAutoPtr.h"

+#include "nsIStreamLoader.h"

+

+#include "nsCOMPtr.h"

+#include "nsError.h"

+#include "nsProxyRelease.h"

+#include "nsString.h"

+

+#include "mozilla/DebugOnly.h"

+#include "mozilla/ErrorResult.h"

+#include "mozilla/dom/Promise.h"

+#include "mozilla/dom/FetchStreamReader.h"

+// Fix X11 header brain damage that conflicts with HeadersGuardEnum::None

+#undef None

+#include "mozilla/dom/RequestBinding.h"

+

+class nsIGlobalObject;

+class nsIEventTarget;

+

+namespace mozilla {

+namespace dom {

+

+class BlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrUSVString;

+class BlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrReadableStreamOrUSVString;

+class BlobImpl;

+class InternalRequest;

+class OwningBlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrUSVString;

+struct ReadableStream;

+class RequestOrUSVString;

+

+namespace workers {

+class WorkerPrivate;

+} // namespace workers

+

+already_AddRefed<Promise>

+FetchRequest(nsIGlobalObject* aGlobal, const RequestOrUSVString& aInput,

+             const RequestInit& aInit, ErrorResult& aRv);

+

+nsresult

+UpdateRequestReferrer(nsIGlobalObject* aGlobal, InternalRequest* aRequest);

+

+/* Deal with unwieldy long webIDL-generated type names */

+namespace fetch {

+  typedef BlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrUSVString BodyInit;

+  typedef BlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrReadableStreamOrUSVString ResponseBodyInit;

+  typedef OwningBlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrUSVString OwningBodyInit;

+};

+

+/*

+ * Creates an nsIInputStream based on the fetch specifications 'extract a byte

+ * stream algorithm' - http://fetch.spec.whatwg.org/#concept-bodyinit-extract.

+ * Stores content type in out param aContentType.

+ */

+nsresult

+ExtractByteStreamFromBody(const fetch::OwningBodyInit& aBodyInit,

+                          nsIInputStream** aStream,

+                          nsCString& aContentType,

+                          uint64_t& aContentLength);

+

+/*

+ * Non-owning version.

+ */

+nsresult

+ExtractByteStreamFromBody(const fetch::BodyInit& aBodyInit,

+                          nsIInputStream** aStream,

+                          nsCString& aContentType,

+                          uint64_t& aContentLength);

+

+/*

+ * Non-owning version. This method should go away when BodyInit will contain

+ * ReadableStream.

+ */

+nsresult

+ExtractByteStreamFromBody(const fetch::ResponseBodyInit& aBodyInit,

+                          nsIInputStream** aStream,

+                          nsCString& aContentType,

+                          uint64_t& aContentLength);

+

+template <class Derived> class FetchBodyConsumer;

+

+enum FetchConsumeType

+{

+  CONSUME_ARRAYBUFFER,

+  CONSUME_BLOB,

+  CONSUME_FORMDATA,

+  CONSUME_JSON,

+  CONSUME_TEXT,

+};

+

+class FetchStreamHolder

+{

+public:

+  NS_IMETHOD_(MozExternalRefCountType) AddRef(void) = 0;

+  NS_IMETHOD_(MozExternalRefCountType) Release(void) = 0;

+

+  virtual void NullifyStream() = 0;

+

+  virtual void MarkAsRead() = 0;

+

+  virtual JSObject* ReadableStreamBody() = 0;

+};

+

+/*

+ * FetchBody's body consumption uses nsIInputStreamPump to read from the

+ * underlying stream to a block of memory, which is then adopted by

+ * ContinueConsumeBody() and converted to the right type based on the JS

+ * function called.

+ *

+ * Use of the nsIInputStreamPump complicates things on the worker thread.

+ * The solution used here is similar to WebSockets.

+ * The difference is that we are only interested in completion and not data

+ * events, and nsIInputStreamPump can only deliver completion on the main thread.

+ *

+ * Before starting the pump on the main thread, we addref the FetchBody to keep

+ * it alive. Then we add a feature, to track the status of the worker.

+ *

+ * ContinueConsumeBody() is the function that cleans things up in both success

+ * and error conditions and so all callers call it with the appropriate status.

+ *

+ * Once the read is initiated on the main thread there are two possibilities.

+ *

+ * 1) Pump finishes before worker has finished Running.

+ *    In this case we adopt the data and dispatch a runnable to the worker,

+ *    which derefs FetchBody and removes the feature and resolves the Promise.

+ *

+ * 2) Pump still working while worker has stopped Running.

+ *    The feature is Notify()ed and ContinueConsumeBody() is called with

+ *    NS_BINDING_ABORTED. We first Cancel() the pump using a sync runnable to

+ *    ensure that mFetchBody remains alive (since mConsumeBodyPump is strongly

+ *    held by it) until pump->Cancel() is called. OnStreamComplete() will not

+ *    do anything if the error code is NS_BINDING_ABORTED, so we don't have to

+ *    worry about keeping anything alive.

+ *

+ * The pump is always released on the main thread.

+ */

+template <class Derived>

+class FetchBody : public FetchStreamHolder

+{

+public:

+  friend class FetchBodyConsumer<Derived>;

+

+  bool

+  BodyUsed() const;

+

+  already_AddRefed<Promise>

+  ArrayBuffer(JSContext* aCx, ErrorResult& aRv)

+  {

+    return ConsumeBody(aCx, CONSUME_ARRAYBUFFER, aRv);

+  }

+

+  already_AddRefed<Promise>

+  Blob(JSContext* aCx, ErrorResult& aRv)

+  {

+    return ConsumeBody(aCx, CONSUME_BLOB, aRv);

+  }

+

+  already_AddRefed<Promise>

+  FormData(JSContext* aCx, ErrorResult& aRv)

+  {

+    return ConsumeBody(aCx, CONSUME_FORMDATA, aRv);

+  }

+

+  already_AddRefed<Promise>

+  Json(JSContext* aCx, ErrorResult& aRv)

+  {

+    return ConsumeBody(aCx, CONSUME_JSON, aRv);

+  }

+

+  already_AddRefed<Promise>

+  Text(JSContext* aCx, ErrorResult& aRv)

+  {

+    return ConsumeBody(aCx, CONSUME_TEXT, aRv);

+  }

+

+  void

+  GetBody(JSContext* aCx,

+          JS::MutableHandle<JSObject*> aBodyOut,

+          ErrorResult& aRv);

+

+  // If the body contains a ReadableStream body object, this method produces a

+  // tee() of it.

+  void

+  MaybeTeeReadableStreamBody(JSContext* aCx,

+                             JS::MutableHandle<JSObject*> aBodyOut,

+                             FetchStreamReader** aStreamReader,

+                             nsIInputStream** aInputStream,

+                             ErrorResult& aRv);

+

+  // Utility public methods accessed by various runnables.

+

+  // This method _must_ be called in order to set the body as used. If the body

+  // is a ReadableStream, this method will start reading the stream.

+  // More in details, this method does:

+  // 1) It uses an internal flag to track if the body is used.  This is tracked

+  // separately from the ReadableStream disturbed state due to purely native

+  // streams.

+  // 2) If there is a ReadableStream reflector for the native stream it is

+  // Locked.

+  // 3) If there is a JS ReadableStream then we begin pumping it into the native

+  // body stream.  This effectively locks and disturbs the stream.

+  //

+  // Note that JSContext is used only if there is a ReadableStream (this can

+  // happen because the body is a ReadableStream or because attribute body has

+  // already been used by content). If something goes wrong using

+  // ReadableStream, errors will be reported via ErrorResult and not as JS

+  // exceptions in JSContext. This is done in order to have a centralized error

+  // reporting way.

+  //

+  // Exceptions generated when reading from the ReadableStream are directly sent

+  // to the Console.

+  void

+  SetBodyUsed(JSContext* aCx, ErrorResult& aRv);

+

+  const nsCString&

+  MimeType() const

+  {

+    return mMimeType;

+  }

+

+  // FetchStreamHolder

+  void

+  NullifyStream() override

+  {

+    mReadableStreamBody = nullptr;

+    mReadableStreamReader = nullptr;

+    mFetchStreamReader = nullptr;

+  }

+

+  JSObject*

+  ReadableStreamBody() override

+  {

+    MOZ_ASSERT(mReadableStreamBody);

+    return mReadableStreamBody;

+  }

+

+  void

+  MarkAsRead() override

+  {

+    mBodyUsed = true;

+  }

+

+  virtual AbortSignal*

+  GetSignal() const = 0;

+

+protected:

+  nsCOMPtr<nsIGlobalObject> mOwner;

+

+  explicit FetchBody(nsIGlobalObject* aOwner);

+

+  // Always set whenever the FetchBody is created on the worker thread.

+  workers::WorkerPrivate* mWorkerPrivate;

+

+  // This is the ReadableStream exposed to content. Its underlying source is a FetchStream object.

+  JS::Heap<JSObject*> mReadableStreamBody;

+

+  // This is the Reader used to retrieve data from the body.

+  JS::Heap<JSObject*> mReadableStreamReader;

+  RefPtr<FetchStreamReader> mFetchStreamReader;

+

+  virtual ~FetchBody();

+

+  void

+  SetMimeType();

+

+  void

+  SetReadableStreamBody(JSObject* aBody);

+

+private:

+  Derived*

+  DerivedClass() const

+  {

+    return static_cast<Derived*>(const_cast<FetchBody*>(this));

+  }

+

+  already_AddRefed<Promise>

+  ConsumeBody(JSContext* aCx, FetchConsumeType aType, ErrorResult& aRv);

+

+  void

+  LockStream(JSContext* aCx, JS::HandleObject aStream, ErrorResult& aRv);

+

+  bool

+  IsOnTargetThread()

+  {

+    return NS_IsMainThread() == !mWorkerPrivate;

+  }

+

+  void

+  AssertIsOnTargetThread()

+  {

+    MOZ_ASSERT(IsOnTargetThread());

+  }

+

+  // Only ever set once, always on target thread.

+  bool mBodyUsed;

+  nsCString mMimeType;

+

+  // The main-thread event target for runnable dispatching.

+  nsCOMPtr<nsIEventTarget> mMainThreadEventTarget;

+};

+

+} // namespace dom

+} // namespace mozilla

+

+#endif // mozilla_dom_Fetch_h

diff --git a/dom/fetch/FetchStream.cpp b/dom/fetch/FetchStream.cpp
new file mode 100644
index 0000000000..1c22a71405
--- /dev/null
+++ b/dom/fetch/FetchStream.cpp
@@ -0,0 +1,640 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FetchStream.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/Maybe.h"
+#include "nsNetCID.h"
+#include "nsITransport.h"
+#include "nsIStreamTransportService.h"
+#include "nsProxyRelease.h"
+#include "WorkerPrivate.h"
+#include "WorkerRunnable.h"
+#include "Workers.h"
+
+#include "mozilla/dom/DOMError.h"
+
+#define FETCH_STREAM_FLAG 0
+
+static NS_DEFINE_CID(kStreamTransportServiceCID,
+                     NS_STREAMTRANSPORTSERVICE_CID);
+
+namespace mozilla {
+namespace dom {
+
+using namespace workers;
+
+namespace {
+
+class FetchStreamWorkerHolder final : public WorkerHolder
+{
+public:
+  explicit FetchStreamWorkerHolder(FetchStream* aStream)
+    : WorkerHolder()
+    , mStream(aStream)
+    , mWasNotified(false)
+  {}
+
+  bool Notify(Status aStatus) override
+  {
+    if (!mWasNotified) {
+      mWasNotified = true;
+      mStream->Close();
+    }
+
+    return true;
+  }
+
+  WorkerPrivate* GetWorkerPrivate() const
+  {
+    return mWorkerPrivate;
+  }
+
+private:
+  RefPtr<FetchStream> mStream;
+  bool mWasNotified;
+};
+
+class FetchStreamWorkerHolderShutdown final : public WorkerControlRunnable
+{
+public:
+  FetchStreamWorkerHolderShutdown(WorkerPrivate* aWorkerPrivate,
+                                  UniquePtr<WorkerHolder>&& aHolder,
+                                  nsCOMPtr<nsIGlobalObject>&& aGlobal,
+                                  RefPtr<FetchStreamHolder>&& aStreamHolder)
+    : WorkerControlRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount)
+    , mHolder(Move(aHolder))
+    , mGlobal(Move(aGlobal))
+    , mStreamHolder(Move(aStreamHolder))
+  {}
+
+  bool
+  WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override
+  {
+    mHolder = nullptr;
+    mGlobal = nullptr;
+
+    mStreamHolder->NullifyStream();
+    mStreamHolder = nullptr;
+
+    return true;
+  }
+
+  // This runnable starts from a JS Thread. We need to disable a couple of
+  // assertions by overriding the following methods.
+
+  bool
+  PreDispatch(WorkerPrivate* aWorkerPrivate) override
+  {
+    return true;
+  }
+
+  void
+  PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override
+  {}
+
+private:
+  UniquePtr<WorkerHolder> mHolder;
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  RefPtr<FetchStreamHolder> mStreamHolder;
+};
+
+} // anonymous
+
+NS_IMPL_ISUPPORTS(FetchStream, nsIInputStreamCallback, nsIObserver,
+                  nsISupportsWeakReference)
+
+/* static */ void
+FetchStream::Create(JSContext* aCx, FetchStreamHolder* aStreamHolder,
+                    nsIGlobalObject* aGlobal, nsIInputStream* aInputStream,
+                    JS::MutableHandle<JSObject*> aStream, ErrorResult& aRv)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aCx);
+  MOZ_DIAGNOSTIC_ASSERT(aInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(aStreamHolder);
+
+  RefPtr<FetchStream> stream = new FetchStream(aGlobal, aStreamHolder, aInputStream);
+
+  if (NS_IsMainThread()) {
+    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+    if (NS_WARN_IF(!os)) {
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+    }
+
+    aRv = os->AddObserver(stream, DOM_WINDOW_DESTROYED_TOPIC, true);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+  } else {
+    WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+    MOZ_ASSERT(workerPrivate);
+
+    UniquePtr<FetchStreamWorkerHolder> holder(
+      new FetchStreamWorkerHolder(stream));
+    if (NS_WARN_IF(!holder->HoldWorker(workerPrivate, Closing))) {
+      aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+      return;
+    }
+
+    // Note, this will create a ref-cycle between the holder and the stream.
+    // The cycle is broken when the stream is closed or the worker begins
+    // shutting down.
+    stream->mWorkerHolder = Move(holder);
+  }
+
+  if (!JS::HasReadableStreamCallbacks(aCx)) {
+    JS::SetReadableStreamCallbacks(aCx,
+                                   &FetchStream::RequestDataCallback,
+                                   &FetchStream::WriteIntoReadRequestCallback,
+                                   &FetchStream::CancelCallback,
+                                   &FetchStream::ClosedCallback,
+                                   &FetchStream::ErroredCallback,
+                                   &FetchStream::FinalizeCallback);
+  }
+
+  JS::Rooted<JSObject*> body(aCx,
+    JS::NewReadableExternalSourceStreamObject(aCx, stream, FETCH_STREAM_FLAG));
+  if (!body) {
+    aRv.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  // This will be released in FetchStream::FinalizeCallback().  We are
+  // guaranteed the jsapi will call FinalizeCallback when ReadableStream
+  // js object is finalized.
+  NS_ADDREF(stream.get());
+
+  aStream.set(body);
+}
+
+/* static */ void
+FetchStream::RequestDataCallback(JSContext* aCx,
+                                 JS::HandleObject aStream,
+                                 void* aUnderlyingSource,
+                                 uint8_t aFlags,
+                                 size_t aDesiredSize)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+  MOZ_DIAGNOSTIC_ASSERT(JS::ReadableStreamIsDisturbed(aStream));
+
+  RefPtr<FetchStream> stream = static_cast<FetchStream*>(aUnderlyingSource);
+  stream->AssertIsOnOwningThread();
+
+  MutexAutoLock lock(stream->mMutex);
+
+  MOZ_DIAGNOSTIC_ASSERT(stream->mState == eInitializing ||
+                        stream->mState == eWaiting ||
+                        stream->mState == eChecking ||
+                        stream->mState == eReading);
+
+  if (stream->mState == eReading) {
+    // We are already reading data.
+    return;
+  }
+
+  if (stream->mState == eChecking) {
+    // If we are looking for more data, there is nothing else we should do:
+    // let's move this checking operation in a reading.
+    MOZ_ASSERT(stream->mInputStream);
+    stream->mState = eReading;
+    return;
+  }
+
+  if (stream->mState == eInitializing) {
+    // The stream has been used for the first time.
+    stream->mStreamHolder->MarkAsRead();
+  }
+
+  stream->mState = eReading;
+
+  if (!stream->mInputStream) {
+    // This is the first use of the stream. Let's convert the
+    // mOriginalInputStream into an nsIAsyncInputStream.
+    MOZ_ASSERT(stream->mOriginalInputStream);
+
+    bool nonBlocking = false;
+    nsresult rv = stream->mOriginalInputStream->IsNonBlocking(&nonBlocking);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      stream->ErrorPropagation(aCx, lock, aStream, rv);
+      return;
+    }
+
+    nsCOMPtr<nsIAsyncInputStream> asyncStream =
+      do_QueryInterface(stream->mOriginalInputStream);
+    if (!nonBlocking || !asyncStream) {
+      nsCOMPtr<nsIStreamTransportService> sts =
+        do_GetService(kStreamTransportServiceCID, &rv);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        stream->ErrorPropagation(aCx, lock, aStream, rv);
+        return;
+      }
+
+      nsCOMPtr<nsITransport> transport;
+      rv = sts->CreateInputTransport(stream->mOriginalInputStream,
+                                     /* aStartOffset */ 0,
+                                     /* aReadLimit */ -1,
+                                     /* aCloseWhenDone */ true,
+                                     getter_AddRefs(transport));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        stream->ErrorPropagation(aCx, lock, aStream, rv);
+        return;
+      }
+
+      nsCOMPtr<nsIInputStream> wrapper;
+      rv = transport->OpenInputStream(/* aFlags */ 0,
+                                       /* aSegmentSize */ 0,
+                                       /* aSegmentCount */ 0,
+                                       getter_AddRefs(wrapper));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        stream->ErrorPropagation(aCx, lock, aStream, rv);
+        return;
+      }
+
+      asyncStream = do_QueryInterface(wrapper);
+    }
+
+    stream->mInputStream = asyncStream;
+    stream->mOriginalInputStream = nullptr;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(stream->mInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(!stream->mOriginalInputStream);
+
+  nsresult rv =
+    stream->mInputStream->AsyncWait(stream, 0, 0, stream->mOwningEventTarget);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    stream->ErrorPropagation(aCx, lock, aStream, rv);
+    return;
+  }
+
+  // All good.
+}
+
+/* static */ void
+FetchStream::WriteIntoReadRequestCallback(JSContext* aCx,
+                                          JS::HandleObject aStream,
+                                          void* aUnderlyingSource,
+                                          uint8_t aFlags, void* aBuffer,
+                                          size_t aLength, size_t* aByteWritten)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+  MOZ_DIAGNOSTIC_ASSERT(aBuffer);
+  MOZ_DIAGNOSTIC_ASSERT(aByteWritten);
+
+  RefPtr<FetchStream> stream = static_cast<FetchStream*>(aUnderlyingSource);
+  stream->AssertIsOnOwningThread();
+
+  MutexAutoLock lock(stream->mMutex);
+
+  MOZ_DIAGNOSTIC_ASSERT(stream->mInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(stream->mState == eWriting);
+  stream->mState = eChecking;
+
+  uint32_t written;
+  nsresult rv =
+    stream->mInputStream->Read(static_cast<char*>(aBuffer), aLength, &written);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    stream->ErrorPropagation(aCx, lock, aStream, rv);
+    return;
+  }
+
+  *aByteWritten = written;
+
+  if (written == 0) {
+    stream->CloseAndReleaseObjects(aCx, lock, aStream);
+    return;
+  }
+
+  rv = stream->mInputStream->AsyncWait(stream, 0, 0, stream->mOwningEventTarget);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    stream->ErrorPropagation(aCx, lock, aStream, rv);
+    return;
+  }
+
+  // All good.
+}
+
+/* static */ JS::Value
+FetchStream::CancelCallback(JSContext* aCx, JS::HandleObject aStream,
+                            void* aUnderlyingSource, uint8_t aFlags,
+                            JS::HandleValue aReason)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+
+  // This is safe because we created an extra reference in FetchStream::Create()
+  // that won't be released until FetchStream::FinalizeCallback() is called.
+  // We are guaranteed that won't happen until the js ReadableStream object
+  // is finalized.
+  FetchStream* stream = static_cast<FetchStream*>(aUnderlyingSource);
+  stream->AssertIsOnOwningThread();
+
+  if (stream->mInputStream) {
+    stream->mInputStream->CloseWithStatus(NS_BASE_STREAM_CLOSED);
+  }
+
+  stream->ReleaseObjects();
+
+  return JS::UndefinedValue();
+}
+
+/* static */ void
+FetchStream::ClosedCallback(JSContext* aCx, JS::HandleObject aStream,
+                            void* aUnderlyingSource, uint8_t aFlags)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+}
+
+/* static */ void
+FetchStream::ErroredCallback(JSContext* aCx, JS::HandleObject aStream,
+                             void* aUnderlyingSource, uint8_t aFlags,
+                             JS::HandleValue aReason)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+
+  // This is safe because we created an extra reference in FetchStream::Create()
+  // that won't be released until FetchStream::FinalizeCallback() is called.
+  // We are guaranteed that won't happen until the js ReadableStream object
+  // is finalized.
+  FetchStream* stream = static_cast<FetchStream*>(aUnderlyingSource);
+  stream->AssertIsOnOwningThread();
+
+  if (stream->mState == eInitializing) {
+    // The stream has been used for the first time.
+    stream->mStreamHolder->MarkAsRead();
+  }
+
+  if (stream->mInputStream) {
+    stream->mInputStream->CloseWithStatus(NS_BASE_STREAM_CLOSED);
+  }
+
+  stream->ReleaseObjects();
+}
+
+void
+FetchStream::FinalizeCallback(void* aUnderlyingSource, uint8_t aFlags)
+{
+  MOZ_DIAGNOSTIC_ASSERT(aUnderlyingSource);
+  MOZ_DIAGNOSTIC_ASSERT(aFlags == FETCH_STREAM_FLAG);
+
+  // This can be called in any thread.
+
+  // This takes ownership of the ref created in FetchStream::Create().
+  RefPtr<FetchStream> stream =
+    dont_AddRef(static_cast<FetchStream*>(aUnderlyingSource));
+
+  stream->ReleaseObjects();
+}
+
+FetchStream::FetchStream(nsIGlobalObject* aGlobal,
+                         FetchStreamHolder* aStreamHolder,
+                         nsIInputStream* aInputStream)
+  : mMutex("FetchStream::mMutex")
+  , mState(eInitializing)
+  , mGlobal(aGlobal)
+  , mStreamHolder(aStreamHolder)
+  , mOriginalInputStream(aInputStream)
+  // TODO: Replace with mGlobal->EventTargetFor(TaskCategory::Other)
+  // When we have the Dispatcher API in the tree, see Issue #1442
+  , mOwningEventTarget(NS_GetCurrentThread())
+{
+  MOZ_DIAGNOSTIC_ASSERT(aInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(aStreamHolder);
+}
+
+FetchStream::~FetchStream()
+{
+}
+
+void
+FetchStream::ErrorPropagation(JSContext* aCx,
+                              const MutexAutoLock& aProofOfLock,
+                              JS::HandleObject aStream,
+                              nsresult aError)
+{
+  AssertIsOnOwningThread();
+
+  // Nothing to do.
+  if (mState == eClosed) {
+    return;
+  }
+
+  // Let's close the stream.
+  if (aError == NS_BASE_STREAM_CLOSED) {
+    CloseAndReleaseObjects(aCx, aProofOfLock, aStream);
+    return;
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mGlobal);
+
+  // Let's use a generic error.
+  RefPtr<DOMError> error = new DOMError(window, NS_ERROR_DOM_TYPE_ERR);
+
+  JS::Rooted<JS::Value> errorValue(aCx);
+  if (ToJSValue(aCx, error, &errorValue)) {
+    MutexAutoUnlock unlock(mMutex);
+    JS::ReadableStreamError(aCx, aStream, errorValue);
+  }
+
+  ReleaseObjects(aProofOfLock);
+}
+
+NS_IMETHODIMP
+FetchStream::OnInputStreamReady(nsIAsyncInputStream* aStream)
+{
+  AssertIsOnOwningThread();
+  MOZ_DIAGNOSTIC_ASSERT(aStream);
+
+  Maybe<MutexAutoLock> lock;
+  lock.emplace(mMutex);
+
+  // Already closed. We have nothing else to do here.
+  if (mState == eClosed) {
+    return NS_OK;
+  }
+
+  nsAutoMicroTask mt;
+  AutoEntryScript aes(mGlobal, "fetch body data available");
+
+  MOZ_DIAGNOSTIC_ASSERT(mInputStream);
+  MOZ_DIAGNOSTIC_ASSERT(mState == eReading || mState == eChecking);
+  
+  JSContext* cx = aes.cx();
+  JS::Rooted<JSObject*> stream(cx, mStreamHolder->ReadableStreamBody());
+
+  uint64_t size = 0;
+  nsresult rv = mInputStream->Available(&size);
+  if (NS_SUCCEEDED(rv) && size == 0) {
+    // In theory this should not happen. If size is 0, the stream should be
+    // considered closed.
+    rv = NS_BASE_STREAM_CLOSED;
+  }
+
+  // No warning for stream closed.
+  if (rv == NS_BASE_STREAM_CLOSED || NS_WARN_IF(NS_FAILED(rv))) {
+    ErrorPropagation(cx, *lock, stream, rv);
+    return NS_OK;
+  }
+
+  // This extra checking is completed. Let's wait for the next read request.
+  if (mState == eChecking) {
+    mState = eWaiting;
+    return NS_OK;
+  }
+
+  mState = eWriting;
+
+  lock.reset();
+
+  JS::ReadableStreamUpdateDataAvailableFromSource(cx, stream, size);
+
+  return NS_OK;
+}
+
+/* static */ nsresult
+FetchStream::RetrieveInputStream(void* aUnderlyingReadableStreamSource,
+                                 nsIInputStream** aInputStream)
+{
+  MOZ_ASSERT(aUnderlyingReadableStreamSource);
+  MOZ_ASSERT(aInputStream);
+
+  RefPtr<FetchStream> stream =
+    static_cast<FetchStream*>(aUnderlyingReadableStreamSource);
+  stream->AssertIsOnOwningThread();
+
+  // if mOriginalInputStream is null, the reading already started. We don't want
+  // to expose the internal inputStream.
+  if (NS_WARN_IF(!stream->mOriginalInputStream)) {
+    return NS_ERROR_DOM_INVALID_STATE_ERR;
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream = stream->mOriginalInputStream;
+  inputStream.forget(aInputStream);
+  return NS_OK;
+}
+
+void
+FetchStream::Close()
+{
+  AssertIsOnOwningThread();
+
+  MutexAutoLock lock(mMutex);
+
+  if (mState == eClosed) {
+    return;
+  }
+
+  AutoJSAPI jsapi;
+  if (NS_WARN_IF(!jsapi.Init(mGlobal))) {
+    ReleaseObjects(lock);
+    return;
+  }
+
+  JSContext* cx = jsapi.cx();
+  JS::Rooted<JSObject*> stream(cx, mStreamHolder->ReadableStreamBody());
+
+  CloseAndReleaseObjects(cx, lock, stream);
+}
+
+void
+FetchStream::CloseAndReleaseObjects(JSContext* aCx,
+                                    const MutexAutoLock& aProofOfLock,
+                                    JS::HandleObject aStream)
+{
+  AssertIsOnOwningThread();
+  MOZ_DIAGNOSTIC_ASSERT(mState != eClosed);
+
+  ReleaseObjects(aProofOfLock);
+ 
+  MutexAutoUnlock unlock(mMutex);
+
+  if (JS::ReadableStreamIsReadable(aStream)) {
+    JS::ReadableStreamClose(aCx, aStream);
+  }
+}
+
+void
+FetchStream::ReleaseObjects()
+{
+  MutexAutoLock lock(mMutex);
+  ReleaseObjects(lock);
+}
+
+void
+FetchStream::ReleaseObjects(const MutexAutoLock& aProofOfLock)
+{
+  // This method can be called on 2 possible threads: the owning one and a JS
+  // thread used to release resources. If we are on the JS thread, we need to
+  // dispatch a runnable to go back to the owning thread in order to release
+  // resources correctly.
+
+  if (mState == eClosed) {
+    // Already gone. Nothing to do.
+    return;
+  }
+
+  mState = eClosed;
+
+  if (mWorkerHolder) {
+    RefPtr<FetchStreamWorkerHolderShutdown> r =
+      new FetchStreamWorkerHolderShutdown(
+        static_cast<FetchStreamWorkerHolder*>(mWorkerHolder.get())->GetWorkerPrivate(),
+        Move(mWorkerHolder), Move(mGlobal), Move(mStreamHolder));
+    r->Dispatch();
+  } else {
+    RefPtr<FetchStream> self = this;
+    RefPtr<Runnable> r = NS_NewRunnableFunction(
+      [self] () {
+        nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+        if (os) {
+          os->RemoveObserver(self, DOM_WINDOW_DESTROYED_TOPIC);
+        }
+        self->mGlobal = nullptr;
+
+        self->mStreamHolder->NullifyStream();
+        self->mStreamHolder = nullptr;
+      });
+
+    NS_DispatchToMainThread(r);
+  }
+}
+
+#ifdef DEBUG
+void
+FetchStream::AssertIsOnOwningThread()
+{
+  NS_ASSERT_OWNINGTHREAD(FetchStream);
+}
+#endif
+
+// nsIObserver
+// -----------
+
+NS_IMETHODIMP
+FetchStream::Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData)
+{
+  AssertIsOnMainThread();
+  AssertIsOnOwningThread();
+
+  MOZ_ASSERT(strcmp(aTopic, DOM_WINDOW_DESTROYED_TOPIC) == 0);
+
+  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mGlobal);
+  if (SameCOMIdentity(aSubject, window)) {
+    Close();
+  }
+
+  return NS_OK;
+}
+
+} // dom namespace
+} // mozilla namespace
diff --git a/dom/fetch/FetchStream.h b/dom/fetch/FetchStream.h
new file mode 100644
index 0000000000..66e1de5642
--- /dev/null
+++ b/dom/fetch/FetchStream.h
@@ -0,0 +1,158 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FetchStream_h
+#define mozilla_dom_FetchStream_h
+
+#include "Fetch.h"
+#include "jsapi.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIObserver.h"
+#include "nsISupportsImpl.h"
+#include "nsWeakReference.h"
+
+class nsIGlobalObject;
+
+class nsIInputStream;
+
+namespace mozilla {
+namespace dom {
+
+namespace workers {
+class WorkerHolder;
+}
+
+class FetchStreamHolder;
+
+class FetchStream final : public nsIInputStreamCallback
+                        , public nsIObserver
+                        , public nsSupportsWeakReference
+{
+public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIINPUTSTREAMCALLBACK
+  NS_DECL_NSIOBSERVER
+
+  static void
+  Create(JSContext* aCx, FetchStreamHolder* aStreamHolder,
+         nsIGlobalObject* aGlobal, nsIInputStream* aInputStream,
+         JS::MutableHandle<JSObject*> aStream, ErrorResult& aRv);
+
+  void
+  Close();
+
+  static nsresult
+  RetrieveInputStream(void* aUnderlyingReadableStreamSource,
+                      nsIInputStream** aInputStream);
+private:
+  FetchStream(nsIGlobalObject* aGlobal,
+              FetchStreamHolder* aStreamHolder,
+              nsIInputStream* aInputStream);
+  ~FetchStream();
+
+#ifdef DEBUG
+  void
+  AssertIsOnOwningThread();
+#else
+  void
+  AssertIsOnOwningThread() {}
+#endif
+
+  static void
+  RequestDataCallback(JSContext* aCx, JS::HandleObject aStream,
+                      void* aUnderlyingSource, uint8_t aFlags,
+                      size_t aDesiredSize);
+
+  static void
+  WriteIntoReadRequestCallback(JSContext* aCx, JS::HandleObject aStream,
+                               void* aUnderlyingSource, uint8_t aFlags,
+                               void* aBuffer, size_t aLength,
+                               size_t* aByteWritten);
+
+  static JS::Value
+  CancelCallback(JSContext* aCx, JS::HandleObject aStream,
+                 void* aUnderlyingSource, uint8_t aFlags,
+                 JS::HandleValue aReason);
+
+  static void
+  ClosedCallback(JSContext* aCx, JS::HandleObject aStream,
+                 void* aUnderlyingSource, uint8_t aFlags);
+
+  static void
+  ErroredCallback(JSContext* aCx, JS::HandleObject aStream,
+                  void* aUnderlyingSource, uint8_t aFlags,
+                  JS::HandleValue reason);
+
+  static void
+  FinalizeCallback(void* aUnderlyingSource, uint8_t aFlags);
+
+  void
+  ErrorPropagation(JSContext* aCx,
+                   const MutexAutoLock& aProofOfLock,
+                   JS::HandleObject aStream, nsresult aRv);
+
+  void
+  CloseAndReleaseObjects(JSContext* aCx,
+                         const MutexAutoLock& aProofOfLock,
+                         JS::HandleObject aSteam);
+
+  class WorkerShutdown;
+
+  void
+  ReleaseObjects(const MutexAutoLock& aProofOfLock);
+
+  void
+  ReleaseObjects();
+
+  // Common methods
+
+  enum State {
+    // This is the beginning state before any reading operation.
+    eInitializing,
+
+    // RequestDataCallback has not been called yet. We haven't started to read
+    // data from the stream yet.
+    eWaiting,
+
+    // We are reading data in a separate I/O thread.
+    eReading,
+
+    // We are ready to write something in the JS Buffer.
+    eWriting,
+
+    // After a writing, we want to check if the stream is closed. After the
+    // check, we go back to eWaiting. If a reading request happens in the
+    // meantime, we move to eReading state.
+    eChecking,
+
+    // Operation completed.
+    eClosed,
+  };
+
+  // We need a mutex because JS engine can release FetchStream on a non-owning
+  // thread. We must be sure that the releasing of resources doesn't trigger
+  // race conditions.
+  Mutex mMutex;
+
+  // Protected by mutex.
+  State mState;
+
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  RefPtr<FetchStreamHolder> mStreamHolder;
+  nsCOMPtr<nsIEventTarget> mOwningEventTarget;
+
+  // This is the original inputStream received during the CTOR. It will be
+  // converted into an nsIAsyncInputStream and stored into mInputStream at the
+  // first use.
+  nsCOMPtr<nsIInputStream> mOriginalInputStream;
+  nsCOMPtr<nsIAsyncInputStream> mInputStream;
+
+  UniquePtr<workers::WorkerHolder> mWorkerHolder;
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_FetchStream_h
diff --git a/dom/fetch/FetchStreamReader.cpp b/dom/fetch/FetchStreamReader.cpp
new file mode 100644
index 0000000000..c6f5ca4d1d
--- /dev/null
+++ b/dom/fetch/FetchStreamReader.cpp
@@ -0,0 +1,405 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FetchStreamReader.h"
+#include "InternalResponse.h"
+#include "mozilla/dom/PromiseBinding.h"
+#include "mozilla/dom/DOMException.h"
+#include "nsContentUtils.h"
+#include "nsIScriptError.h"
+#include "nsPIDOMWindow.h"
+
+namespace mozilla {
+namespace dom {
+
+using namespace workers;
+
+namespace {
+
+class FetchStreamReaderWorkerHolder final : public WorkerHolder
+{
+public:
+  explicit FetchStreamReaderWorkerHolder(FetchStreamReader* aReader)
+    : WorkerHolder(WorkerHolder::Behavior::AllowIdleShutdownStart)
+    , mReader(aReader)
+    , mWasNotified(false)
+  {}
+
+  bool Notify(Status aStatus) override
+  {
+    if (!mWasNotified) {
+      mWasNotified = true;
+      // The WorkerPrivate does have a context available, and we could pass it
+      // here to trigger cancellation of the reader, but the author of this
+      // comment chickened out.
+      mReader->CloseAndRelease(nullptr, NS_ERROR_DOM_INVALID_STATE_ERR);
+    }
+
+    return true;
+  }
+
+private:
+  RefPtr<FetchStreamReader> mReader;
+  bool mWasNotified;
+};
+
+} // anonymous
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FetchStreamReader)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FetchStreamReader)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(FetchStreamReader)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(FetchStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReader)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FetchStreamReader)
+  NS_INTERFACE_MAP_ENTRY(nsIOutputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIOutputStreamCallback)
+NS_INTERFACE_MAP_END
+
+/* static */ nsresult
+FetchStreamReader::Create(JSContext* aCx, nsIGlobalObject* aGlobal,
+                          FetchStreamReader** aStreamReader,
+                          nsIInputStream** aInputStream)
+{
+  MOZ_ASSERT(aCx);
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(aStreamReader);
+  MOZ_ASSERT(aInputStream);
+
+  RefPtr<FetchStreamReader> streamReader = new FetchStreamReader(aGlobal);
+
+  nsCOMPtr<nsIAsyncInputStream> pipeIn;
+
+  nsresult rv = NS_NewPipe2(getter_AddRefs(pipeIn),
+                            getter_AddRefs(streamReader->mPipeOut),
+                            true, true, 0, 0);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!NS_IsMainThread()) {
+    WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+    MOZ_ASSERT(workerPrivate);
+
+    // We need to know when the worker goes away.
+    UniquePtr<FetchStreamReaderWorkerHolder> holder(
+      new FetchStreamReaderWorkerHolder(streamReader));
+    if (NS_WARN_IF(!holder->HoldWorker(workerPrivate, Closing))) {
+      streamReader->mPipeOut->CloseWithStatus(NS_ERROR_DOM_INVALID_STATE_ERR);
+      return NS_ERROR_DOM_INVALID_STATE_ERR;
+    }
+
+    // These 2 objects create a ref-cycle here that is broken when the stream is
+    // closed or the worker shutsdown.
+    streamReader->mWorkerHolder = Move(holder);
+  }
+
+  pipeIn.forget(aInputStream);
+  streamReader.forget(aStreamReader);
+  return NS_OK;
+}
+
+FetchStreamReader::FetchStreamReader(nsIGlobalObject* aGlobal)
+  : mGlobal(aGlobal)
+  // TODO: Replace with mGlobal->EventTargetFor(TaskCategory::Other)
+  // When we have the Dispatcher API in the tree, see Issue #1442
+  , mOwningEventTarget(NS_GetCurrentThread())
+  , mBufferRemaining(0)
+  , mBufferOffset(0)
+  , mStreamClosed(false)
+{
+  MOZ_ASSERT(aGlobal);
+}
+
+FetchStreamReader::~FetchStreamReader()
+{
+  CloseAndRelease(nullptr, NS_BASE_STREAM_CLOSED);
+}
+
+// If a context is provided, an attempt will be made to cancel the reader.  The
+// only situation where we don't expect to have a context is when closure is
+// being triggered from the destructor or the WorkerHolder is notifying.  If
+// we're at the destructor, it's far too late to cancel anything.  And if the
+// WorkerHolder is being notified, the global is going away, so there's also
+// no need to do further JS work.
+void
+FetchStreamReader::CloseAndRelease(JSContext* aCx, nsresult aStatus)
+{
+  NS_ASSERT_OWNINGTHREAD(FetchStreamReader);
+
+  if (mStreamClosed) {
+    // Already closed.
+    return;
+  }
+
+  RefPtr<FetchStreamReader> kungFuDeathGrip = this;
+
+  if (aCx) {
+    MOZ_ASSERT(mReader);
+
+    RefPtr<DOMException> error = DOMException::Create(aStatus);
+
+    JS::Rooted<JS::Value> errorValue(aCx);
+    if (ToJSValue(aCx, error, &errorValue)) {
+      JS::Rooted<JSObject*> reader(aCx, mReader);
+      // It's currently safe to cancel an already closed reader because, per the
+      // comments in ReadableStream::cancel() conveying the spec, step 2 of
+      // 3.4.3 that specified ReadableStreamCancel is: If stream.[[state]] is
+      // "closed", return a new promise resolved with undefined.
+      JS::ReadableStreamReaderCancel(aCx, reader, errorValue);
+    }
+  }
+  mStreamClosed = true;
+
+  mGlobal = nullptr;
+
+  mPipeOut->CloseWithStatus(aStatus);
+  mPipeOut = nullptr;
+
+  mWorkerHolder = nullptr;
+
+  mReader = nullptr;
+  mBuffer = nullptr;
+}
+
+void
+FetchStreamReader::StartConsuming(JSContext* aCx,
+                                  JS::HandleObject aStream,
+                                  JS::MutableHandle<JSObject*> aReader,
+                                  ErrorResult& aRv)
+{
+  MOZ_DIAGNOSTIC_ASSERT(!mReader);
+  MOZ_DIAGNOSTIC_ASSERT(aStream);
+
+  JS::Rooted<JSObject*> reader(aCx,
+                               JS::ReadableStreamGetReader(aCx, aStream,
+                                                           JS::ReadableStreamReaderMode::Default));
+  if (!reader) {
+    aRv.StealExceptionFromJSContext(aCx);
+    CloseAndRelease(aCx, NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  mReader = reader;
+  aReader.set(reader);
+
+  aRv = mPipeOut->AsyncWait(this, 0, 0, mOwningEventTarget);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+}
+
+// nsIOutputStreamCallback interface
+
+NS_IMETHODIMP
+FetchStreamReader::OnOutputStreamReady(nsIAsyncOutputStream* aStream)
+{
+  NS_ASSERT_OWNINGTHREAD(FetchStreamReader);
+  MOZ_ASSERT(aStream == mPipeOut);
+  MOZ_ASSERT(mReader);
+
+  if (mStreamClosed) {
+    return NS_OK;
+  }
+
+  if (mBuffer) {
+    return WriteBuffer();
+  }
+
+  // TODO: We need to verify this is the correct global per the spec.
+  //       See bug 1385890.
+  AutoEntryScript aes(mGlobal, "ReadableStreamReader.read", !mWorkerHolder);
+
+  JS::Rooted<JSObject*> reader(aes.cx(), mReader);
+  JS::Rooted<JSObject*> promise(aes.cx(),
+                                JS::ReadableStreamDefaultReaderRead(aes.cx(),
+                                                                    reader));
+  if (NS_WARN_IF(!promise)) {
+    // Let's close the stream.
+    CloseAndRelease(aes.cx(), NS_ERROR_DOM_INVALID_STATE_ERR);
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<Promise> domPromise = Promise::CreateFromExisting(mGlobal, promise);
+  if (NS_WARN_IF(!domPromise)) {
+    // Let's close the stream.
+    CloseAndRelease(aes.cx(), NS_ERROR_DOM_INVALID_STATE_ERR);
+    return NS_ERROR_FAILURE;
+  }
+
+  // Let's wait.
+  domPromise->AppendNativeHandler(this);
+  return NS_OK;
+}
+
+void
+FetchStreamReader::ResolvedCallback(JSContext* aCx,
+                                    JS::Handle<JS::Value> aValue)
+{
+  if (mStreamClosed) {
+    return;
+  }
+
+  // This promise should be resolved with { done: boolean, value: something },
+  // "value" is interesting only if done is false.
+
+  // We don't want to play with JS api, let's WebIDL bindings doing it for us.
+  // FetchReadableStreamReadDataDone is a dictionary with just a boolean, if the
+  // parsing succeeded, we can proceed with the parsing of the "value", which it
+  // must be a Uint8Array.
+  FetchReadableStreamReadDataDone valueDone;
+  if (!valueDone.Init(aCx, aValue)) {
+    JS_ClearPendingException(aCx);
+    CloseAndRelease(aCx, NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  if (valueDone.mDone) {
+    // Stream is completed.
+    CloseAndRelease(aCx, NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  UniquePtr<FetchReadableStreamReadDataArray> value(
+    new FetchReadableStreamReadDataArray);
+  if (!value->Init(aCx, aValue) || !value->mValue.WasPassed()) {
+    JS_ClearPendingException(aCx);
+    CloseAndRelease(aCx, NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  Uint8Array& array = value->mValue.Value();
+  array.ComputeLengthAndData();
+  uint32_t len = array.Length();
+
+  if (len == 0) {
+    // If there is nothing to read, let's do another reading.
+    OnOutputStreamReady(mPipeOut);
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(!mBuffer);
+  mBuffer = Move(value);
+
+  mBufferOffset = 0;
+  mBufferRemaining = len;
+
+  nsresult rv = WriteBuffer();
+  if (NS_FAILED(rv)) {
+    // DOMException only understands errors from domerr.msg, so we normalize to
+    // identifying an abort if the write fails.
+    CloseAndRelease(aCx, NS_ERROR_DOM_ABORT_ERR);
+  }
+}
+
+nsresult
+FetchStreamReader::WriteBuffer()
+{
+  MOZ_ASSERT(mBuffer);
+  MOZ_ASSERT(mBuffer->mValue.WasPassed());
+
+  Uint8Array& array = mBuffer->mValue.Value();
+  char* data = reinterpret_cast<char*>(array.Data());
+
+  while (1) {
+    uint32_t written = 0;
+    nsresult rv =
+      mPipeOut->Write(data + mBufferOffset, mBufferRemaining, &written);
+
+    if (rv == NS_BASE_STREAM_WOULD_BLOCK) {
+      break;
+    }
+
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    MOZ_ASSERT(written <= mBufferRemaining);
+    mBufferRemaining -= written;
+    mBufferOffset += written;
+
+    if (mBufferRemaining == 0) {
+      mBuffer = nullptr;
+      break;
+    }
+  }
+
+  nsresult rv = mPipeOut->AsyncWait(this, 0, 0, mOwningEventTarget);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+void
+FetchStreamReader::RejectedCallback(JSContext* aCx,
+                                    JS::Handle<JS::Value> aValue)
+{
+  ReportErrorToConsole(aCx, aValue);
+  CloseAndRelease(aCx, NS_ERROR_FAILURE);
+}
+
+void
+FetchStreamReader::ReportErrorToConsole(JSContext* aCx,
+                                        JS::Handle<JS::Value> aValue)
+{
+  nsCString sourceSpec;
+  uint32_t line = 0;
+  uint32_t column = 0;
+  nsString valueString;
+
+  nsContentUtils::ExtractErrorValues(aCx, aValue, sourceSpec, &line,
+                                     &column, valueString);
+
+  nsTArray<nsString> params;
+  params.AppendElement(valueString);
+
+  RefPtr<ConsoleReportCollector> reporter = new ConsoleReportCollector();
+  reporter->AddConsoleReport(nsIScriptError::errorFlag,
+                             NS_LITERAL_CSTRING("ReadableStreamReader.read"),
+                             nsContentUtils::eDOM_PROPERTIES,
+                             sourceSpec, line, column,
+                             NS_LITERAL_CSTRING("ReadableStreamReadingFailed"),
+                             params);
+
+  uint64_t innerWindowId = 0;
+
+  if (NS_IsMainThread()) {
+    nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mGlobal);
+    if (window) {
+      innerWindowId = window->WindowID();
+    }
+    reporter->FlushReportsByWindowId(innerWindowId);
+    return;
+  }
+
+  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+  if (workerPrivate) {
+    innerWindowId = workerPrivate->WindowID();
+  }
+
+  RefPtr<Runnable> r = NS_NewRunnableFunction(
+    [reporter, innerWindowId] () {
+      reporter->FlushReportsByWindowId(innerWindowId);
+    });
+
+  workerPrivate->DispatchToMainThread(r.forget());
+}
+
+} // dom namespace
+} // mozilla namespace
diff --git a/dom/fetch/FetchStreamReader.h b/dom/fetch/FetchStreamReader.h
new file mode 100644
index 0000000000..c25685046c
--- /dev/null
+++ b/dom/fetch/FetchStreamReader.h
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FetchStreamReader_h
+#define mozilla_dom_FetchStreamReader_h
+
+#include "jsapi.h"
+#include "mozilla/dom/FetchBinding.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+#include "nsIAsyncOutputStream.h"
+
+namespace mozilla {
+namespace dom {
+
+namespace workers {
+class WorkerHolder;
+}
+
+class FetchStreamReader final : public nsIOutputStreamCallback
+                              , public PromiseNativeHandler
+{
+public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(FetchStreamReader, nsIOutputStreamCallback)
+  NS_DECL_NSIOUTPUTSTREAMCALLBACK
+
+  // This creates a nsIInputStream able to retrieve data from the ReadableStream
+  // object. The reading starts when StartConsuming() is called.
+  static nsresult
+  Create(JSContext* aCx, nsIGlobalObject* aGlobal,
+         FetchStreamReader** aStreamReader,
+         nsIInputStream** aInputStream);
+
+  void
+  ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue) override;
+
+  void
+  RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue) override;
+
+  // Idempotently close the output stream and null out all state. If aCx is
+  // provided, the reader will also be canceled.  aStatus must be a DOM error
+  // as understood by DOMException because it will be provided as the
+  // cancellation reason.
+  void
+  CloseAndRelease(JSContext* aCx, nsresult aStatus);
+
+  void
+  StartConsuming(JSContext* aCx,
+                 JS::HandleObject aStream,
+                 JS::MutableHandle<JSObject*> aReader,
+                 ErrorResult& aRv);
+
+private:
+  explicit FetchStreamReader(nsIGlobalObject* aGlobal);
+  ~FetchStreamReader();
+
+  nsresult
+  WriteBuffer();
+
+  void
+  ReportErrorToConsole(JSContext* aCx, JS::Handle<JS::Value> aValue);
+
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  nsCOMPtr<nsIEventTarget> mOwningEventTarget;
+
+  nsCOMPtr<nsIAsyncOutputStream> mPipeOut;
+
+  UniquePtr<workers::WorkerHolder> mWorkerHolder;
+
+  JS::Heap<JSObject*> mReader;
+
+  UniquePtr<FetchReadableStreamReadDataArray> mBuffer;
+  uint32_t mBufferRemaining;
+  uint32_t mBufferOffset;
+
+  bool mStreamClosed;
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_FetchStreamReader_h
diff --git a/dom/fetch/InternalResponse.cpp b/dom/fetch/InternalResponse.cpp
index ec32c4e216..f4fd1912f9 100644
--- a/dom/fetch/InternalResponse.cpp
+++ b/dom/fetch/InternalResponse.cpp
@@ -139,18 +139,18 @@ InternalResponse::ToIPC(IPCInternalResponse* aIPCResponse,
 }
 
 already_AddRefed<InternalResponse>
-InternalResponse::Clone()
+InternalResponse::Clone(CloneType aCloneType)
 {
   RefPtr<InternalResponse> clone = CreateIncompleteCopy();
 
   clone->mHeaders = new InternalHeaders(*mHeaders);
   if (mWrappedResponse) {
-    clone->mWrappedResponse = mWrappedResponse->Clone();
+    clone->mWrappedResponse = mWrappedResponse->Clone(aCloneType);
     MOZ_ASSERT(!mBody);
     return clone.forget();
   }
 
-  if (!mBody) {
+  if (!mBody || aCloneType == eDontCloneInputStream) {
     return clone.forget();
   }
 
diff --git a/dom/fetch/InternalResponse.h b/dom/fetch/InternalResponse.h
index e4b4a0ab62..d5c759d577 100644
--- a/dom/fetch/InternalResponse.h
+++ b/dom/fetch/InternalResponse.h
@@ -46,7 +46,13 @@ public:
         M* aManager,
         UniquePtr<mozilla::ipc::AutoIPCStream>& aAutoStream);
 
-  already_AddRefed<InternalResponse> Clone();
+  enum CloneType
+  {
+    eCloneInputStream,
+    eDontCloneInputStream,
+  };
+
+  already_AddRefed<InternalResponse> Clone(CloneType eCloneType);
 
   static already_AddRefed<InternalResponse>
   NetworkError()
diff --git a/dom/fetch/Request.cpp b/dom/fetch/Request.cpp
index ab87a3215a..b79b539772 100644
--- a/dom/fetch/Request.cpp
+++ b/dom/fetch/Request.cpp
@@ -29,7 +29,25 @@ using namespace workers;
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(Request)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(Request)
-NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(Request, mOwner, mHeaders)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(Request)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Request)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mHeaders)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Request)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mHeaders)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Request)
+  MOZ_DIAGNOSTIC_ASSERT(!tmp->mReadableStreamReader);
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReadableStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Request)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
@@ -37,8 +55,7 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Request)
 NS_INTERFACE_MAP_END
 
 Request::Request(nsIGlobalObject* aOwner, InternalRequest* aRequest, AbortSignal* aSignal)
-  : FetchBody<Request>()
-  , mOwner(aOwner)
+  : FetchBody<Request>(aOwner)
   , mRequest(aRequest)
   , mSignal(aSignal)
 {
@@ -557,17 +574,15 @@ Request::Constructor(const GlobalObject& aGlobal,
   }
 
   if (aInit.mBody.WasPassed()) {
-    const Nullable<OwningArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams>& bodyInitNullable =
-      aInit.mBody.Value();
+    const Nullable<fetch::OwningBodyInit>& bodyInitNullable = aInit.mBody.Value();
     if (!bodyInitNullable.IsNull()) {
-      const OwningArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams& bodyInit =
-        bodyInitNullable.Value();
+      const fetch::OwningBodyInit& bodyInit = bodyInitNullable.Value();
       nsCOMPtr<nsIInputStream> stream;
-      nsAutoCString contentType;
+      nsAutoCString contentTypeWithCharset;
       uint64_t contentLengthUnused;
       aRv = ExtractByteStreamFromBody(bodyInit,
                                       getter_AddRefs(stream),
-                                      contentType,
+                                      contentTypeWithCharset,
                                       contentLengthUnused);
       if (NS_WARN_IF(aRv.Failed())) {
         return nullptr;
@@ -575,10 +590,10 @@ Request::Constructor(const GlobalObject& aGlobal,
 
       temporaryBody = stream;
 
-      if (!contentType.IsVoid() &&
+      if (!contentTypeWithCharset.IsVoid() &&
           !requestHeaders->Has(NS_LITERAL_CSTRING("Content-Type"), aRv)) {
         requestHeaders->Append(NS_LITERAL_CSTRING("Content-Type"),
-                               contentType, aRv);
+                               contentTypeWithCharset, aRv);
       }
 
       if (NS_WARN_IF(aRv.Failed())) {
@@ -599,7 +614,10 @@ Request::Constructor(const GlobalObject& aGlobal,
     inputReq->GetBody(getter_AddRefs(body));
     if (body) {
       inputReq->SetBody(nullptr);
-      inputReq->SetBodyUsed();
+      inputReq->SetBodyUsed(aGlobal.Context(), aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return nullptr;
+      }
     }
   }
   return domRequest.forget();
diff --git a/dom/fetch/Request.h b/dom/fetch/Request.h
index 8c01cbd799..d5fc09fe25 100644
--- a/dom/fetch/Request.h
+++ b/dom/fetch/Request.h
@@ -128,6 +128,8 @@ public:
   void
   GetBody(nsIInputStream** aStream) { return mRequest->GetBody(aStream); }
 
+  using FetchBody::GetBody;
+
   void
   SetBody(nsIInputStream* aStream) { return mRequest->SetBody(aStream); }
 
@@ -162,7 +164,6 @@ public:
 private:
   ~Request();
 
-  nsCOMPtr<nsIGlobalObject> mOwner;
   RefPtr<InternalRequest> mRequest;
   
   // Lazily created.
diff --git a/dom/fetch/Response.cpp b/dom/fetch/Response.cpp
index 42b25ae1d9..3ee5e93d4a 100644
--- a/dom/fetch/Response.cpp
+++ b/dom/fetch/Response.cpp
@@ -12,12 +12,16 @@
 
 #include "mozilla/ErrorResult.h"
 #include "mozilla/dom/FetchBinding.h"
+#include "mozilla/dom/ResponseBinding.h"
 #include "mozilla/dom/Headers.h"
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/URL.h"
 
 #include "nsDOMString.h"
 
+#include "BodyExtractor.h"
+#include "FetchStream.h"
+#include "FetchStreamReader.h"
 #include "InternalResponse.h"
 #include "WorkerPrivate.h"
 
@@ -26,7 +30,31 @@ namespace dom {
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(Response)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(Response)
-NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(Response, mOwner, mHeaders)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(Response)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Response)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mHeaders)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mFetchStreamReader)
+
+  tmp->mReadableStreamBody = nullptr;
+  tmp->mReadableStreamReader = nullptr;
+
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Response)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mHeaders)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFetchStreamReader)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Response)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReadableStreamBody)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReadableStreamReader)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Response)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
@@ -34,18 +62,21 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Response)
 NS_INTERFACE_MAP_END
 
 Response::Response(nsIGlobalObject* aGlobal, InternalResponse* aInternalResponse, AbortSignal* aSignal)
-  : FetchBody<Response>()
-  , mOwner(aGlobal)
+  : FetchBody<Response>(aGlobal)
   , mInternalResponse(aInternalResponse)
   , mSignal(aSignal)
 {
   MOZ_ASSERT(aInternalResponse->Headers()->Guard() == HeadersGuardEnum::Immutable ||
              aInternalResponse->Headers()->Guard() == HeadersGuardEnum::Response);
   SetMimeType();
+  
+  // Keep a firm grip!
+  mozilla::HoldJSObjects(this);
 }
 
 Response::~Response()
 {
+  mozilla::DropJSObjects(this);
 }
 
 /* static */ already_AddRefed<Response>
@@ -106,7 +137,7 @@ Response::Redirect(const GlobalObject& aGlobal, const nsAString& aUrl,
     return nullptr;
   }
 
-  Optional<Nullable<ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams>> body;
+  Optional<fetch::ResponseBodyInit> body;
   ResponseInit init;
   init.mStatus = aStatus;
   RefPtr<Response> r = Response::Constructor(aGlobal, body, init, aRv);
@@ -127,7 +158,7 @@ Response::Redirect(const GlobalObject& aGlobal, const nsAString& aUrl,
 
 /*static*/ already_AddRefed<Response>
 Response::Constructor(const GlobalObject& aGlobal,
-                      const Optional<Nullable<ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams>>& aBody,
+                      const Optional<fetch::ResponseBodyInit>& aBody,
                       const ResponseInit& aInit, ErrorResult& aRv)
 {
   nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
@@ -193,29 +224,86 @@ Response::Constructor(const GlobalObject& aGlobal,
     }
   }
 
-  if (aBody.WasPassed() && !aBody.Value().IsNull()) {
+  if (aBody.WasPassed()) {
     if (aInit.mStatus == 204 || aInit.mStatus == 205 || aInit.mStatus == 304) {
       aRv.ThrowTypeError<MSG_RESPONSE_NULL_STATUS_WITH_BODY>();
       return nullptr;
     }
 
+    nsCString contentTypeWithCharset;
     nsCOMPtr<nsIInputStream> bodyStream;
-    nsCString contentType;
-    uint64_t bodySize = 0;
-    aRv = ExtractByteStreamFromBody(aBody.Value().Value(),
-                                    getter_AddRefs(bodyStream),
-                                    contentType,
-                                    bodySize);
-    if (NS_WARN_IF(aRv.Failed())) {
-      return nullptr;
+    int64_t bodySize = InternalResponse::UNKNOWN_BODY_SIZE;
+    
+    if (aBody.Value().IsReadableStream()) {
+      const ReadableStream& readableStream =
+        aBody.Value().GetAsReadableStream();
+
+      JS::Rooted<JSObject*> readableStreamObj(aGlobal.Context(),
+                                              readableStream.Obj());
+
+      if (JS::ReadableStreamIsDisturbed(readableStreamObj) ||
+          JS::ReadableStreamIsLocked(readableStreamObj) ||
+          !JS::ReadableStreamIsReadable(readableStreamObj)) {
+        aRv.ThrowTypeError<MSG_FETCH_BODY_CONSUMED_ERROR>();
+        return nullptr;
+      }
+
+      r->SetReadableStreamBody(readableStreamObj);
+
+      if (JS::ReadableStreamGetMode(readableStreamObj) ==
+            JS::ReadableStreamMode::ExternalSource) {
+        // If this is a DOM generated ReadableStream, we can extract the
+        // inputStream directly.
+        void* underlyingSource = nullptr;
+        if (!JS::ReadableStreamGetExternalUnderlyingSource(aGlobal.Context(),
+                                                           readableStreamObj,
+                                                           &underlyingSource)) {
+          aRv.StealExceptionFromJSContext(aGlobal.Context());
+          return nullptr;
+        }
+
+        MOZ_ASSERT(underlyingSource);
+
+        aRv = FetchStream::RetrieveInputStream(underlyingSource,
+                                               getter_AddRefs(bodyStream));
+
+        // The releasing of the external source is needed in order to avoid an
+        // extra stream lock.
+        JS::ReadableStreamReleaseExternalUnderlyingSource(readableStreamObj);
+        if (NS_WARN_IF(aRv.Failed())) {
+          return nullptr;
+        }
+      } else {
+        // If this is a JS-created ReadableStream, let's create a
+        // FetchStreamReader.
+        aRv = FetchStreamReader::Create(aGlobal.Context(), global,
+                                        getter_AddRefs(r->mFetchStreamReader),
+                                        getter_AddRefs(bodyStream));
+        if (NS_WARN_IF(aRv.Failed())) {
+          return nullptr;
+        }
+      }
+    } else {
+      uint64_t size = 0;
+      aRv = ExtractByteStreamFromBody(aBody.Value(),
+                                      getter_AddRefs(bodyStream),
+                                      contentTypeWithCharset,
+                                      size);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return nullptr;
+      }
+
+      bodySize = size;
     }
+    
     internalResponse->SetBody(bodyStream, bodySize);
 
-    if (!contentType.IsVoid() &&
+    if (!contentTypeWithCharset.IsVoid() &&
         !internalResponse->Headers()->Has(NS_LITERAL_CSTRING("Content-Type"), aRv)) {
       // Ignore Append() failing here.
       ErrorResult error;
-      internalResponse->Headers()->Append(NS_LITERAL_CSTRING("Content-Type"), contentType, error);
+      internalResponse->Headers()->Append(NS_LITERAL_CSTRING("Content-Type"),
+                                          contentTypeWithCharset, error);
       error.SuppressException();
     }
 
@@ -229,29 +317,87 @@ Response::Constructor(const GlobalObject& aGlobal,
 }
 
 already_AddRefed<Response>
-Response::Clone(ErrorResult& aRv) const
+Response::Clone(JSContext* aCx, ErrorResult& aRv)
 {
   if (BodyUsed()) {
     aRv.ThrowTypeError<MSG_FETCH_BODY_CONSUMED_ERROR>();
     return nullptr;
   }
 
-  RefPtr<InternalResponse> ir = mInternalResponse->Clone();
-  RefPtr<Response> response = new Response(mOwner, ir, mSignal);
+  RefPtr<FetchStreamReader> streamReader;
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  JS::Rooted<JSObject*> body(aCx);
+  MaybeTeeReadableStreamBody(aCx, &body,
+                             getter_AddRefs(streamReader),
+                             getter_AddRefs(inputStream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT_IF(body, streamReader);
+  MOZ_ASSERT_IF(body, inputStream);
+
+  RefPtr<InternalResponse> ir =
+    mInternalResponse->Clone(body
+      ? InternalResponse::eDontCloneInputStream
+      : InternalResponse::eCloneInputStream);
+
+  RefPtr<Response> response = new Response(mOwner, ir, nullptr);
+
+  if (body) {
+    // Maybe we have a body, but we receive null from MaybeTeeReadableStreamBody
+    // if this body is a native stream. In this case, the InternalResponse will
+    // have a clone of the native body and the ReadableStream will be created
+    // lazily if needed.
+    response->SetReadableStreamBody(body);
+    response->mFetchStreamReader = streamReader;
+    ir->SetBody(inputStream, InternalResponse::UNKNOWN_BODY_SIZE);
+  }
+
   return response.forget();
 }
 
 already_AddRefed<Response>
-Response::CloneUnfiltered(ErrorResult& aRv) const
+Response::CloneUnfiltered(JSContext* aCx, ErrorResult& aRv)
 {
   if (BodyUsed()) {
     aRv.ThrowTypeError<MSG_FETCH_BODY_CONSUMED_ERROR>();
     return nullptr;
   }
 
-  RefPtr<InternalResponse> clone = mInternalResponse->Clone();
+  RefPtr<FetchStreamReader> streamReader;
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  JS::Rooted<JSObject*> body(aCx);
+  MaybeTeeReadableStreamBody(aCx, &body,
+                             getter_AddRefs(streamReader),
+                             getter_AddRefs(inputStream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT_IF(body, streamReader);
+  MOZ_ASSERT_IF(body, inputStream);
+
+  RefPtr<InternalResponse> clone =
+    mInternalResponse->Clone(body
+      ? InternalResponse::eDontCloneInputStream
+      : InternalResponse::eCloneInputStream);
+
   RefPtr<InternalResponse> ir = clone->Unfiltered();
-  RefPtr<Response> ref = new Response(mOwner, ir, mSignal);
+  RefPtr<Response> ref = new Response(mOwner, ir, nullptr);
+
+  if (body) {
+    // Maybe we have a body, but we receive null from MaybeTeeReadableStreamBody
+    // if this body is a native stream. In this case, the InternalResponse will
+    // have a clone of the native body and the ReadableStream will be created
+    // lazily if needed.
+    ref->SetReadableStreamBody(body);
+    ref->mFetchStreamReader = streamReader;
+    ir->SetBody(inputStream, InternalResponse::UNKNOWN_BODY_SIZE);
+  }
+
   return ref.forget();
 }
 
diff --git a/dom/fetch/Response.h b/dom/fetch/Response.h
index fa2ced87d8..d2f885fbc7 100644
--- a/dom/fetch/Response.h
+++ b/dom/fetch/Response.h
@@ -105,6 +105,8 @@ public:
   void
   GetBody(nsIInputStream** aStream) { return mInternalResponse->GetBody(aStream); }
 
+  using FetchBody::GetBody;
+
   static already_AddRefed<Response>
   Error(const GlobalObject& aGlobal);
 
@@ -113,7 +115,7 @@ public:
 
   static already_AddRefed<Response>
   Constructor(const GlobalObject& aGlobal,
-              const Optional<Nullable<ArrayBufferOrArrayBufferViewOrBlobOrFormDataOrUSVStringOrURLSearchParams>>& aBody,
+              const Optional<fetch::ResponseBodyInit>& aBody,
               const ResponseInit& aInit, ErrorResult& rv);
 
   nsIGlobalObject* GetParentObject() const
@@ -122,10 +124,10 @@ public:
   }
 
   already_AddRefed<Response>
-  Clone(ErrorResult& aRv) const;
+  Clone(JSContext* aCx, ErrorResult& aRv);
 
   already_AddRefed<Response>
-  CloneUnfiltered(ErrorResult& aRv) const;
+  CloneUnfiltered(JSContext* aCx, ErrorResult& aRv);
 
   void
   SetBody(nsIInputStream* aBody, int64_t aBodySize);
@@ -142,7 +144,6 @@ public:
 private:
   ~Response();
 
-  nsCOMPtr<nsIGlobalObject> mOwner;
   RefPtr<InternalResponse> mInternalResponse;
 
   // Lazily created
diff --git a/dom/fetch/moz.build b/dom/fetch/moz.build
index d1a8a49323..f01254e042 100644
--- a/dom/fetch/moz.build
+++ b/dom/fetch/moz.build
@@ -4,11 +4,13 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 EXPORTS.mozilla.dom += [
+    'BodyExtractor.h',
     'ChannelInfo.h',
     'Fetch.h',
     'FetchDriver.h',
     'FetchIPCTypes.h',
     'FetchObserver.h',
+    'FetchStreamReader.h',
     'FetchUtil.h',
     'Headers.h',
     'InternalHeaders.h',
@@ -19,11 +21,14 @@ EXPORTS.mozilla.dom += [
 ]
 
 UNIFIED_SOURCES += [
+    'BodyExtractor.cpp',
     'ChannelInfo.cpp',
     'Fetch.cpp',
     'FetchConsumer.cpp',
     'FetchDriver.cpp',
     'FetchObserver.cpp',
+    'FetchStream.cpp',
+    'FetchStreamReader.cpp',
     'FetchUtil.cpp',
     'Headers.cpp',
     'InternalHeaders.cpp',
diff --git a/dom/network/TCPSocketParent.cpp b/dom/network/TCPSocketParent.cpp
index 96eab44510..0e7f0e17ae 100644
--- a/dom/network/TCPSocketParent.cpp
+++ b/dom/network/TCPSocketParent.cpp
@@ -310,7 +310,7 @@ TCPSocketParent::RecvData(const SendableData& aData,
       const nsTArray<uint8_t>& buffer = aData.get_ArrayOfuint8_t();
       bool ok = IPC::DeserializeArrayBuffer(autoCx, buffer, &val);
       NS_ENSURE_TRUE(ok, true);
-      RootedTypedArray<ArrayBuffer> data(autoCx);
+      RootedSpiderMonkeyInterface<ArrayBuffer> data(autoCx);
       data.Init(&val.toObject());
       Optional<uint32_t> byteLength(buffer.Length());
       mSocket->SendWithTrackingNumber(autoCx, data, 0, byteLength, aTrackingNumber, rv);
diff --git a/dom/url/URLSearchParams.cpp b/dom/url/URLSearchParams.cpp
index 3a0311aabd..19cc3cda6b 100644
--- a/dom/url/URLSearchParams.cpp
+++ b/dom/url/URLSearchParams.cpp
@@ -575,9 +575,10 @@ URLSearchParams::ReadStructuredClone(JSStructuredCloneReader* aReader)
 
 NS_IMETHODIMP
 URLSearchParams::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
-                             nsACString& aContentType, nsACString& aCharset)
+                             nsACString& aContentTypeWithCharset,
+                             nsACString& aCharset)
 {
-  aContentType.AssignLiteral("application/x-www-form-urlencoded");
+  aContentTypeWithCharset.AssignLiteral("application/x-www-form-urlencoded;charset=UTF-8");
   aCharset.AssignLiteral("UTF-8");
 
   nsAutoString serialized;
diff --git a/dom/webidl/Fetch.webidl b/dom/webidl/Fetch.webidl
index 4b2a0af7d0..bbb1faf7f7 100644
--- a/dom/webidl/Fetch.webidl
+++ b/dom/webidl/Fetch.webidl
@@ -8,7 +8,7 @@
  */
 
 typedef object JSON;
-typedef (ArrayBuffer or ArrayBufferView or Blob or FormData or USVString or URLSearchParams) BodyInit;
+typedef (Blob or BufferSource or FormData or URLSearchParams or USVString) BodyInit;
 
 [NoInterfaceObject, Exposed=(Window,Worker)]
 interface Body {
@@ -24,3 +24,15 @@ interface Body {
   [Throws]
   Promise<USVString> text();
 };
+
+// These are helper dictionaries for the parsing of a
+// getReader().read().then(data) parsing.
+// See more about how these 2 helpers are used in
+// dom/fetch/FetchStreamReader.cpp
+dictionary FetchReadableStreamReadDataDone {
+  boolean done = false;
+};
+
+dictionary FetchReadableStreamReadDataArray {
+  Uint8Array value;
+};
diff --git a/dom/webidl/Navigator.webidl b/dom/webidl/Navigator.webidl
index 516b5415e3..5f2ac63e1e 100644
--- a/dom/webidl/Navigator.webidl
+++ b/dom/webidl/Navigator.webidl
@@ -296,7 +296,7 @@ partial interface Navigator {
 partial interface Navigator {
   [Throws, Pref="beacon.enabled"]
   boolean sendBeacon(DOMString url,
-                     optional (ArrayBufferView or Blob or DOMString or FormData)? data = null);
+                     optional BodyInit? data = null);
 };
 
 partial interface Navigator {
diff --git a/dom/webidl/Response.webidl b/dom/webidl/Response.webidl
index 08f31fe29a..0f4c99dbac 100644
--- a/dom/webidl/Response.webidl
+++ b/dom/webidl/Response.webidl
@@ -7,7 +7,9 @@
  * https://fetch.spec.whatwg.org/#response-class
  */
 
-[Constructor(optional BodyInit? body, optional ResponseInit init),
+// This should be Constructor(optional BodyInit... but BodyInit doesn't include
+// ReadableStream yet because we don't want to expose the Streams API to Request.
+[Constructor(optional (Blob or BufferSource or FormData or URLSearchParams or ReadableStream or USVString) body, optional ResponseInit init),
  Exposed=(Window,Worker)]
 interface Response {
   [NewObject] static Response error();
@@ -30,6 +32,12 @@ interface Response {
 };
 Response implements Body;
 
+// This should be part of Body but we don't want to expose body to request yet.
+partial interface Response {
+  [GetterThrows, Func="nsContentUtils::StreamsEnabled"]
+  readonly attribute ReadableStream? body;
+};
+
 dictionary ResponseInit {
   unsigned short status = 200;
   ByteString statusText = "OK";
diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
index 239207efc9..6138a3c6de 100644
--- a/dom/workers/RuntimeService.cpp
+++ b/dom/workers/RuntimeService.cpp
@@ -299,6 +299,7 @@ LoadContextOptions(const char* aPrefName, void* /* aClosure */)
                 .setNativeRegExp(GetWorkerPref<bool>(NS_LITERAL_CSTRING("native_regexp")))
                 .setAsyncStack(GetWorkerPref<bool>(NS_LITERAL_CSTRING("asyncstack")))
                 .setWerror(GetWorkerPref<bool>(NS_LITERAL_CSTRING("werror")))
+                .setStreams(GetWorkerPref<bool>(NS_LITERAL_CSTRING("streams")))
                 .setExtraWarnings(GetWorkerPref<bool>(NS_LITERAL_CSTRING("strict")))
                 .setArrayProtoValues(GetWorkerPref<bool>(
                       NS_LITERAL_CSTRING("array_prototype_values")));
diff --git a/dom/workers/ScriptLoader.cpp b/dom/workers/ScriptLoader.cpp
index 5aaac7cfae..bedf966ef1 100644
--- a/dom/workers/ScriptLoader.cpp
+++ b/dom/workers/ScriptLoader.cpp
@@ -700,9 +700,14 @@ private:
     request.SetAsUSVString().Rebind(loadInfo.mFullURL.Data(),
                                     loadInfo.mFullURL.Length());
 
+    // This JSContext will not end up executing JS code because here there are
+    // no ReadableStreams involved.
+    AutoJSAPI jsapi;
+    jsapi.Init();
+
     ErrorResult error;
     RefPtr<Promise> cachePromise =
-      mCacheCreator->Cache_()->Put(request, *response, error);
+      mCacheCreator->Cache_()->Put(jsapi.cx(), request, *response, error);
     if (NS_WARN_IF(error.Failed())) {
       nsresult rv = error.StealNSResult();
       channel->Cancel(rv);
@@ -1667,8 +1672,13 @@ CacheScriptLoader::Load(Cache* aCache)
 
   mozilla::dom::CacheQueryOptions params;
 
+  // This JSContext will not end up executing JS code because here there are
+  // no ReadableStreams involved.
+  AutoJSAPI jsapi;
+  jsapi.Init();
+
   ErrorResult error;
-  RefPtr<Promise> promise = aCache->Match(request, params, error);
+  RefPtr<Promise> promise = aCache->Match(jsapi.cx(), request, params, error);
   if (NS_WARN_IF(error.Failed())) {
     Fail(error.StealNSResult());
     return;
diff --git a/dom/workers/ServiceWorkerEvents.cpp b/dom/workers/ServiceWorkerEvents.cpp
index ce2e5e7aae..569422da25 100644
--- a/dom/workers/ServiceWorkerEvents.cpp
+++ b/dom/workers/ServiceWorkerEvents.cpp
@@ -6,6 +6,7 @@
 #include "ServiceWorkerEvents.h"
 
 #include "nsAutoPtr.h"
+#include "nsContentUtils.h"
 #include "nsIConsoleReportCollector.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsINetworkInterceptController.h"
@@ -30,8 +31,6 @@
 #include "mozilla/Move.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/BodyUtil.h"
-#include "mozilla/dom/DOMException.h"
-#include "mozilla/dom/DOMExceptionBinding.h"
 #include "mozilla/dom/EncodingUtils.h"
 #include "mozilla/dom/FetchEventBinding.h"
 #include "mozilla/dom/MessagePort.h"
@@ -404,76 +403,6 @@ void RespondWithCopyComplete(void* aClosure, nsresult aStatus)
   MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(event));
 }
 
-namespace {
-
-void
-ExtractErrorValues(JSContext* aCx, JS::Handle<JS::Value> aValue,
-                  nsACString& aSourceSpecOut, uint32_t *aLineOut,
-                  uint32_t *aColumnOut, nsString& aMessageOut)
-{
-  MOZ_ASSERT(aLineOut);
-  MOZ_ASSERT(aColumnOut);
-
-  if (aValue.isObject()) {
-    JS::Rooted<JSObject*> obj(aCx, &aValue.toObject());
-    RefPtr<DOMException> domException;
-
-    // Try to process as an Error object.  Use the file/line/column values
-    // from the Error as they will be more specific to the root cause of
-    // the problem.
-    JSErrorReport* err = obj ? JS_ErrorFromException(aCx, obj) : nullptr;
-    if (err) {
-      // Use xpc to extract the error message only.  We don't actually send
-      // this report anywhere.
-      RefPtr<xpc::ErrorReport> report = new xpc::ErrorReport();
-      report->Init(err,
-                   "<unknown>", // toString result
-                   false,       // chrome
-                   0);          // window ID
-
-      if (!report->mFileName.IsEmpty()) {
-        CopyUTF16toUTF8(report->mFileName, aSourceSpecOut);
-        *aLineOut = report->mLineNumber;
-        *aColumnOut = report->mColumn;
-      }
-      aMessageOut.Assign(report->mErrorMsg);
-    }
-
-    // Next, try to unwrap the rejection value as a DOMException.
-    else if(NS_SUCCEEDED(UNWRAP_OBJECT(DOMException, obj, domException))) {
-
-      nsAutoString filename;
-      domException->GetFilename(aCx, filename);
-      if (!filename.IsEmpty()) {
-        CopyUTF16toUTF8(filename, aSourceSpecOut);
-        *aLineOut = domException->LineNumber(aCx);
-        *aColumnOut = domException->ColumnNumber();
-      }
-
-      domException->GetName(aMessageOut);
-      aMessageOut.AppendLiteral(": ");
-
-      nsAutoString message;
-      domException->GetMessageMoz(message);
-      aMessageOut.Append(message);
-    }
-  }
-
-  // If we could not unwrap a specific error type, then perform default safe
-  // string conversions on primitives.  Objects will result in "[Object]"
-  // unfortunately.
-  if (aMessageOut.IsEmpty()) {
-    nsAutoJSString jsString;
-    if (jsString.init(aCx, aValue)) {
-      aMessageOut = jsString;
-    } else {
-      JS_ClearPendingException(aCx);
-    }
-  }
-}
-
-} // anonymous namespace
-
 class MOZ_STACK_CLASS AutoCancel
 {
   RefPtr<RespondWithHandler> mOwner;
@@ -505,6 +434,44 @@ public:
     }
   }
 
+  // This function steals the error message from a ErrorResult.
+  void
+  SetCancelErrorResult(JSContext* aCx, ErrorResult& aRv)
+  {
+    MOZ_DIAGNOSTIC_ASSERT(aRv.Failed());
+    MOZ_DIAGNOSTIC_ASSERT(!JS_IsExceptionPending(aCx));
+
+    // Storing the error as exception in the JSContext.
+    if (!aRv.MaybeSetPendingException(aCx)) {
+      return;
+    }
+
+    MOZ_ASSERT(!aRv.Failed());
+
+    // Let's take the pending exception.
+    JS::Rooted<JS::Value> exn(aCx);
+    if (!JS_GetPendingException(aCx, &exn)) {
+      return;
+    }
+
+    JS_ClearPendingException(aCx);
+
+    // Converting the exception in a js::ErrorReport.
+    js::ErrorReport report(aCx);
+    if (!report.init(aCx, exn, js::ErrorReport::WithSideEffects)) {
+      JS_ClearPendingException(aCx);
+      return;
+    }
+
+    MOZ_ASSERT(mOwner);
+    MOZ_ASSERT(mMessageName.EqualsLiteral("InterceptionFailedWithURL"));
+    MOZ_ASSERT(mParams.Length() == 1);
+
+    // Let's store the error message here.
+    mMessageName.Assign(report.toStringResult().c_str());
+    mParams.Clear();
+  }
+
   template<typename... Params>
   void SetCancelMessage(const nsACString& aMessageName, Params&&... aParams)
   {
@@ -557,7 +524,8 @@ RespondWithHandler::ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValu
     uint32_t line = 0;
     uint32_t column = 0;
     nsString valueString;
-    ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column, valueString);
+    nsContentUtils::ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column,
+                                       valueString);
 
     autoCancel.SetCancelMessageAndLocation(sourceSpec, line, column,
                                            NS_LITERAL_CSTRING("InterceptedNonResponseWithURL"),
@@ -572,7 +540,8 @@ RespondWithHandler::ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValu
     uint32_t line = 0;
     uint32_t column = 0;
     nsString valueString;
-    ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column, valueString);
+    nsContentUtils::ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column,
+                                       valueString);
 
     autoCancel.SetCancelMessageAndLocation(sourceSpec, line, column,
                                            NS_LITERAL_CSTRING("InterceptedNonResponseWithURL"),
@@ -659,7 +628,12 @@ RespondWithHandler::ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValu
   ir->GetUnfilteredBody(getter_AddRefs(body));
   // Errors and redirects may not have a body.
   if (body) {
-    response->SetBodyUsed();
+    IgnoredErrorResult error;
+    response->SetBodyUsed(aCx, error);
+    if (NS_WARN_IF(error.Failed())) {
+      autoCancel.SetCancelErrorResult(aCx, error);
+      return;
+    }
 
     nsCOMPtr<nsIOutputStream> responseBody;
     rv = mInterceptedChannel->GetResponseBody(getter_AddRefs(responseBody));
@@ -715,7 +689,8 @@ RespondWithHandler::RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValu
   uint32_t column = mRespondWithColumnNumber;
   nsString valueString;
 
-  ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column, valueString);
+  nsContentUtils::ExtractErrorValues(aCx, aValue, sourceSpec, &line, &column,
+                                     valueString);
 
   ::AsyncLog(mInterceptedChannel, sourceSpec, line, column,
              NS_LITERAL_CSTRING("InterceptionRejectedResponseWithURL"),
@@ -853,7 +828,8 @@ public:
     nsCString spec;
     uint32_t line = 0;
     uint32_t column = 0;
-    ExtractErrorValues(aCx, aValue, spec, &line, &column, mRejectValue);
+    nsContentUtils::ExtractErrorValues(aCx, aValue, spec, &line, &column,
+                                       mRejectValue);
 
     // only use the extracted location if we found one
     if (!spec.IsEmpty()) {
diff --git a/dom/workers/ServiceWorkerScriptCache.cpp b/dom/workers/ServiceWorkerScriptCache.cpp
index 05be250da8..f343c35586 100644
--- a/dom/workers/ServiceWorkerScriptCache.cpp
+++ b/dom/workers/ServiceWorkerScriptCache.cpp
@@ -395,7 +395,7 @@ public:
         return;
       }
 
-      WriteToCache(cache);
+      WriteToCache(aCx, cache);
       return;
     }
 
@@ -528,7 +528,7 @@ private:
   }
 
   void
-  WriteToCache(Cache* aCache)
+  WriteToCache(JSContext* aCx, Cache* aCache)
   {
     AssertIsOnMainThread();
     MOZ_ASSERT(aCache);
@@ -561,8 +561,10 @@ private:
     // For now we have to wait until the Put Promise is fulfilled before we can
     // continue since Cache does not yet support starting a read that is being
     // written to.
-    RefPtr<Promise> cachePromise = aCache->Put(request, *response, result);
+    RefPtr<Promise> cachePromise = aCache->Put(aCx, request, *response, result);
     if (NS_WARN_IF(result.Failed())) {
+      // No exception here because there are no ReadableStreams involved here.
+      MOZ_ASSERT(!result.IsJSException());
       MOZ_ASSERT(!result.IsErrorWithMessage());
       Fail(result.StealNSResult());
       return;
@@ -903,7 +905,7 @@ CompareCache::ManageCacheResult(JSContext* aCx, JS::Handle<JS::Value> aValue)
   request.SetAsUSVString().Rebind(mURL.Data(), mURL.Length());
   ErrorResult error;
   CacheQueryOptions params;
-  RefPtr<Promise> promise = cache->Match(request, params, error);
+  RefPtr<Promise> promise = cache->Match(aCx, request, params, error);
   if (NS_WARN_IF(error.Failed())) {
     mManager->CacheFinished(error.StealNSResult(), false);
     return;
diff --git a/dom/workers/WorkerHolder.cpp b/dom/workers/WorkerHolder.cpp
index 5a8c5c4d8f..dcdcd29fa3 100644
--- a/dom/workers/WorkerHolder.cpp
+++ b/dom/workers/WorkerHolder.cpp
@@ -8,8 +8,9 @@
 
 BEGIN_WORKERS_NAMESPACE
 
-WorkerHolder::WorkerHolder()
+WorkerHolder::WorkerHolder(Behavior aBehavior)
   : mWorkerPrivate(nullptr)
+  , mBehavior(aBehavior)
 {
 }
 
@@ -44,6 +45,12 @@ WorkerHolder::ReleaseWorker()
   ReleaseWorkerInternal();
 }
 
+WorkerHolder::Behavior
+WorkerHolder::GetBehavior() const
+{
+  return mBehavior;
+}
+
 void
 WorkerHolder::ReleaseWorkerInternal()
 {
diff --git a/dom/workers/WorkerHolder.h b/dom/workers/WorkerHolder.h
index 050c6f8e20..d8f3927af7 100644
--- a/dom/workers/WorkerHolder.h
+++ b/dom/workers/WorkerHolder.h
@@ -73,7 +73,12 @@ class WorkerHolder
 public:
   NS_DECL_OWNINGTHREAD
 
-  WorkerHolder();
+  enum Behavior {
+    AllowIdleShutdownStart,
+    PreventIdleShutdownStart,
+  };
+
+  explicit WorkerHolder(Behavior aBehavior = PreventIdleShutdownStart);
   virtual ~WorkerHolder();
 
   bool HoldWorker(WorkerPrivate* aWorkerPrivate, Status aFailStatus);
@@ -81,6 +86,8 @@ public:
 
   virtual bool Notify(Status aStatus) = 0;
 
+  Behavior GetBehavior() const;
+
 protected:
   void ReleaseWorkerInternal();
 
@@ -88,6 +95,8 @@ protected:
 
 private:
   void AssertIsOwningThread() const;
+
+  const Behavior mBehavior;
 };
 
 END_WORKERS_NAMESPACE
diff --git a/dom/workers/WorkerPrefs.h b/dom/workers/WorkerPrefs.h
index 215b375ddb..415435cf06 100644
--- a/dom/workers/WorkerPrefs.h
+++ b/dom/workers/WorkerPrefs.h
@@ -35,6 +35,7 @@ WORKER_SIMPLE_PREF("dom.serviceWorkers.testing.enabled", ServiceWorkersTestingEn
 WORKER_SIMPLE_PREF("dom.serviceWorkers.openWindow.enabled", OpenWindowEnabled, OPEN_WINDOW_ENABLED)
 WORKER_SIMPLE_PREF("dom.storageManager.enabled", StorageManagerEnabled, STORAGEMANAGER_ENABLED)
 WORKER_SIMPLE_PREF("dom.push.enabled", PushEnabled, PUSH_ENABLED)
+WORKER_SIMPLE_PREF("dom.streams.enabled", StreamsEnabled, STREAMS_ENABLED)
 WORKER_SIMPLE_PREF("dom.requestcontext.enabled", RequestContextEnabled, REQUESTCONTEXT_ENABLED)
 WORKER_SIMPLE_PREF("gfx.offscreencanvas.enabled", OffscreenCanvasEnabled, OFFSCREENCANVAS_ENABLED)
 WORKER_SIMPLE_PREF("dom.webkitBlink.dirPicker.enabled", WebkitBlinkDirectoryPickerEnabled, DOM_WEBKITBLINK_DIRPICKER_WEBKITBLINK)
diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index 622a882a65..3b3de7e3b5 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -4154,6 +4154,7 @@ WorkerPrivate::WorkerPrivate(WorkerPrivate* aParent,
   , mDebugger(nullptr)
   , mJSContext(nullptr)
   , mPRThread(nullptr)
+  , mNumHoldersPreventingShutdownStart(0)
   , mDebuggerEventLoopLevel(0)
   , mMainThreadEventTarget(do_GetMainThread())
   , mErrorHandlerRecursionCount(0)
@@ -5382,8 +5383,11 @@ WorkerPrivate::AddHolder(WorkerHolder* aHolder, Status aFailStatus)
 
   MOZ_ASSERT(!mHolders.Contains(aHolder), "Already know about this one!");
 
-  if (mHolders.IsEmpty() && !ModifyBusyCountFromWorker(true)) {
-    return false;
+  if (aHolder->GetBehavior() == WorkerHolder::PreventIdleShutdownStart) {
+    if (!mNumHoldersPreventingShutdownStart && !ModifyBusyCountFromWorker(true)) {
+      return false;
+    }
+    mNumHoldersPreventingShutdownStart += 1;
   }
 
   mHolders.AppendElement(aHolder);
@@ -5398,8 +5402,11 @@ WorkerPrivate::RemoveHolder(WorkerHolder* aHolder)
   MOZ_ASSERT(mHolders.Contains(aHolder), "Didn't know about this one!");
   mHolders.RemoveElement(aHolder);
 
-  if (mHolders.IsEmpty() && !ModifyBusyCountFromWorker(false)) {
-    NS_WARNING("Failed to modify busy count!");
+  if (aHolder->GetBehavior() == WorkerHolder::PreventIdleShutdownStart) {
+    mNumHoldersPreventingShutdownStart -= 1;
+    if (!mNumHoldersPreventingShutdownStart && !ModifyBusyCountFromWorker(false)) {
+      NS_WARNING("Failed to modify busy count!");
+    }
   }
 }
 
diff --git a/dom/workers/WorkerPrivate.h b/dom/workers/WorkerPrivate.h
index 9effdccc9a..26afecb69b 100644
--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -980,6 +980,7 @@ class WorkerPrivate : public WorkerPrivateParent<WorkerPrivate>
   RefPtr<WorkerDebuggerGlobalScope> mDebuggerScope;
   nsTArray<ParentType*> mChildWorkers;
   nsTObserverArray<WorkerHolder*> mHolders;
+  uint32_t mNumHoldersPreventingShutdownStart;
   nsTArray<nsAutoPtr<TimeoutInfo>> mTimeouts;
   uint32_t mDebuggerEventLoopLevel;
   RefPtr<ThrottledEventQueue> mMainThreadThrottledEventQueue;
diff --git a/dom/xhr/XMLHttpRequestMainThread.cpp b/dom/xhr/XMLHttpRequestMainThread.cpp
index d97476ef61..a89af3c370 100644
--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -2298,175 +2298,6 @@ XMLHttpRequestMainThread::ChangeStateToDone()
   }
 }
 
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<nsIDocument>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  nsCOMPtr<nsIDOMDocument> domdoc(do_QueryInterface(mBody));
-  NS_ENSURE_STATE(domdoc);
-  aCharset.AssignLiteral("UTF-8");
-
-  nsresult rv;
-  nsCOMPtr<nsIStorageStream> storStream;
-  rv = NS_NewStorageStream(4096, UINT32_MAX, getter_AddRefs(storStream));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsCOMPtr<nsIOutputStream> output;
-  rv = storStream->GetOutputStream(0, getter_AddRefs(output));
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  if (mBody->IsHTMLDocument()) {
-    aContentType.AssignLiteral("text/html");
-
-    nsString serialized;
-    if (!nsContentUtils::SerializeNodeToMarkup(mBody, true, serialized)) {
-      return NS_ERROR_OUT_OF_MEMORY;
-    }
-
-    nsAutoCString utf8Serialized;
-    if (!AppendUTF16toUTF8(serialized, utf8Serialized, fallible)) {
-      return NS_ERROR_OUT_OF_MEMORY;
-    }
-
-    uint32_t written;
-    rv = output->Write(utf8Serialized.get(), utf8Serialized.Length(), &written);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    MOZ_ASSERT(written == utf8Serialized.Length());
-  } else {
-    aContentType.AssignLiteral("application/xml");
-
-    nsCOMPtr<nsIDOMSerializer> serializer =
-      do_CreateInstance(NS_XMLSERIALIZER_CONTRACTID, &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    // Make sure to use the encoding we'll send
-    rv = serializer->SerializeToStream(domdoc, output, aCharset);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-
-  output->Close();
-
-  uint32_t length;
-  rv = storStream->GetLength(&length);
-  NS_ENSURE_SUCCESS(rv, rv);
-  *aContentLength = length;
-
-  rv = storStream->NewInputStream(0, aResult);
-  NS_ENSURE_SUCCESS(rv, rv);
-  return NS_OK;
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<const nsAString>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  aContentType.AssignLiteral("text/plain");
-  aCharset.AssignLiteral("UTF-8");
-
-  nsAutoCString converted;
-  if (!AppendUTF16toUTF8(*mBody, converted, fallible)) {
-    return NS_ERROR_OUT_OF_MEMORY;
-  }
-
-  *aContentLength = converted.Length();
-  nsresult rv = NS_NewCStringInputStream(aResult, converted);
-  NS_ENSURE_SUCCESS(rv, rv);
-  return NS_OK;
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<nsIInputStream>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  aContentType.AssignLiteral("text/plain");
-  aCharset.Truncate();
-
-  nsresult rv = mBody->Available(aContentLength);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  nsCOMPtr<nsIInputStream> stream(mBody);
-  stream.forget(aResult);
-  return NS_OK;
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<Blob>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  return mBody->GetSendInfo(aResult, aContentLength, aContentType, aCharset);
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<FormData>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  return mBody->GetSendInfo(aResult, aContentLength, aContentType, aCharset);
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<URLSearchParams>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  return mBody->GetSendInfo(aResult, aContentLength, aContentType, aCharset);
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<nsIXHRSendable>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  return mBody->GetSendInfo(aResult, aContentLength, aContentType, aCharset);
-}
-
-static nsresult
-GetBufferDataAsStream(const uint8_t* aData, uint32_t aDataLength,
-                      nsIInputStream** aResult, uint64_t* aContentLength,
-                      nsACString& aContentType, nsACString& aCharset)
-{
-  aContentType.SetIsVoid(true);
-  aCharset.Truncate();
-
-  *aContentLength = aDataLength;
-  const char* data = reinterpret_cast<const char*>(aData);
-
-  nsCOMPtr<nsIInputStream> stream;
-  nsresult rv = NS_NewByteInputStream(getter_AddRefs(stream), data, aDataLength,
-                                      NS_ASSIGNMENT_COPY);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  stream.forget(aResult);
-
-  return NS_OK;
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<const ArrayBuffer>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  mBody->ComputeLengthAndData();
-  return GetBufferDataAsStream(mBody->Data(), mBody->Length(),
-                               aResult, aContentLength, aContentType, aCharset);
-}
-
-template<> nsresult
-XMLHttpRequestMainThread::RequestBody<const ArrayBufferView>::GetAsStream(
-   nsIInputStream** aResult, uint64_t* aContentLength,
-   nsACString& aContentType, nsACString& aCharset) const
-{
-  mBody->ComputeLengthAndData();
-  return GetBufferDataAsStream(mBody->Data(), mBody->Length(),
-                               aResult, aContentLength, aContentType, aCharset);
-}
-
-
 nsresult
 XMLHttpRequestMainThread::CreateChannel()
 {
@@ -2792,7 +2623,7 @@ XMLHttpRequestMainThread::Send(nsIVariant* aVariant)
     // document?
     nsCOMPtr<nsIDocument> doc = do_QueryInterface(supports);
     if (doc) {
-      RequestBody<nsIDocument> body(doc);
+      BodyExtractor<nsIDocument> body(doc);
       return SendInternal(&body);
     }
 
@@ -2801,21 +2632,21 @@ XMLHttpRequestMainThread::Send(nsIVariant* aVariant)
     if (wstr) {
       nsAutoString string;
       wstr->GetData(string);
-      RequestBody<const nsAString> body(&string);
+      BodyExtractor<const nsAString> body(&string);
       return SendInternal(&body);
     }
 
     // nsIInputStream?
     nsCOMPtr<nsIInputStream> stream = do_QueryInterface(supports);
     if (stream) {
-      RequestBody<nsIInputStream> body(stream);
+      BodyExtractor<nsIInputStream> body(stream);
       return SendInternal(&body);
     }
 
     // nsIXHRSendable?
     nsCOMPtr<nsIXHRSendable> sendable = do_QueryInterface(supports);
     if (sendable) {
-      RequestBody<nsIXHRSendable> body(sendable);
+      BodyExtractor<nsIXHRSendable> body(sendable);
       return SendInternal(&body);
     }
 
@@ -2826,9 +2657,9 @@ XMLHttpRequestMainThread::Send(nsIVariant* aVariant)
     nsresult rv = aVariant->GetAsJSVal(&realVal);
     if (NS_SUCCEEDED(rv) && !realVal.isPrimitive()) {
       JS::Rooted<JSObject*> obj(rootingCx, realVal.toObjectOrNull());
-      RootedTypedArray<ArrayBuffer> buf(rootingCx);
+      RootedSpiderMonkeyInterface<ArrayBuffer> buf(rootingCx);
       if (buf.Init(obj)) {
-        RequestBody<const ArrayBuffer> body(&buf);
+        BodyExtractor<const ArrayBuffer> body(&buf);
         return SendInternal(&body);
       }
     }
@@ -2845,12 +2676,12 @@ XMLHttpRequestMainThread::Send(nsIVariant* aVariant)
   nsString string;
   string.Adopt(data, len);
 
-  RequestBody<const nsAString> body(&string);
+  BodyExtractor<const nsAString> body(&string);
   return SendInternal(&body);
 }
 
 nsresult
-XMLHttpRequestMainThread::SendInternal(const RequestBodyBase* aBody)
+XMLHttpRequestMainThread::SendInternal(const BodyExtractorBase* aBody)
 {
   NS_ENSURE_TRUE(mPrincipal, NS_ERROR_NOT_INITIALIZED);
 
@@ -2916,13 +2747,6 @@ XMLHttpRequestMainThread::SendInternal(const RequestBodyBase* aBody)
       mAuthorRequestHeaders.Get("content-type", uploadContentType);
       if (uploadContentType.IsVoid()) {
         uploadContentType = defaultContentType;
-
-        if (!charset.IsEmpty()) {
-          // If we are providing the default content type, then we also need to
-          // provide a charset declaration.
-          uploadContentType.Append(NS_LITERAL_CSTRING(";charset="));
-          uploadContentType.Append(charset);
-        }
       }
 
       // We don't want to set a charset for streams.
diff --git a/dom/xhr/XMLHttpRequestMainThread.h b/dom/xhr/XMLHttpRequestMainThread.h
index 4a6eeec2ef..f2145605ef 100644
--- a/dom/xhr/XMLHttpRequestMainThread.h
+++ b/dom/xhr/XMLHttpRequestMainThread.h
@@ -34,7 +34,11 @@
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/NotNull.h"
 #include "mozilla/dom/MutableBlobStorage.h"
+#include "mozilla/dom/BodyExtractor.h"
 #include "mozilla/dom/TypedArray.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FormData.h"
+#include "mozilla/dom/URLSearchParams.h"
 #include "mozilla/dom/XMLHttpRequest.h"
 #include "mozilla/dom/XMLHttpRequestBinding.h"
 #include "mozilla/dom/XMLHttpRequestEventTarget.h"
@@ -54,11 +58,8 @@ class nsIJSID;
 namespace mozilla {
 namespace dom {
 
-class Blob;
 class BlobSet;
 class DOMString;
-class FormData;
-class URLSearchParams;
 class XMLHttpRequestUpload;
 struct OriginAttributesDictionary;
 
@@ -288,34 +289,7 @@ public:
 private:
   virtual ~XMLHttpRequestMainThread();
 
-  class RequestBodyBase
-  {
-  public:
-    virtual nsresult GetAsStream(nsIInputStream** aResult,
-                                 uint64_t* aContentLength,
-                                 nsACString& aContentType,
-                                 nsACString& aCharset) const
-    {
-      NS_ASSERTION(false, "RequestBodyBase should not be used directly.");
-      return NS_ERROR_FAILURE;
-    }
-  };
-
-  template<typename Type>
-  class RequestBody final : public RequestBodyBase
-  {
-    Type* mBody;
-  public:
-    explicit RequestBody(Type* aBody) : mBody(aBody)
-    {
-    }
-    nsresult GetAsStream(nsIInputStream** aResult,
-                         uint64_t* aContentLength,
-                         nsACString& aContentType,
-                         nsACString& aCharset) const override;
-  };
-
-  nsresult SendInternal(const RequestBodyBase* aBody);
+  nsresult SendInternal(const BodyExtractorBase* aBody);
 
   bool IsCrossSiteCORSRequest() const;
   bool IsDeniedCrossSiteCORSRequest();
@@ -336,7 +310,7 @@ public:
   Send(JSContext* /*aCx*/, const ArrayBuffer& aArrayBuffer,
        ErrorResult& aRv) override
   {
-    RequestBody<const ArrayBuffer> body(&aArrayBuffer);
+    BodyExtractor<const ArrayBuffer> body(&aArrayBuffer);
     aRv = SendInternal(&body);
   }
 
@@ -344,28 +318,28 @@ public:
   Send(JSContext* /*aCx*/, const ArrayBufferView& aArrayBufferView,
        ErrorResult& aRv) override
   {
-    RequestBody<const ArrayBufferView> body(&aArrayBufferView);
+    BodyExtractor<const ArrayBufferView> body(&aArrayBufferView);
     aRv = SendInternal(&body);
   }
 
   virtual void
   Send(JSContext* /*aCx*/, Blob& aBlob, ErrorResult& aRv) override
   {
-    RequestBody<Blob> body(&aBlob);
+    BodyExtractor<nsIXHRSendable> body(&aBlob);
     aRv = SendInternal(&body);
   }
 
   virtual void Send(JSContext* /*aCx*/, URLSearchParams& aURLSearchParams,
                     ErrorResult& aRv) override
   {
-    RequestBody<URLSearchParams> body(&aURLSearchParams);
+    BodyExtractor<nsIXHRSendable> body(&aURLSearchParams);
     aRv = SendInternal(&body);
   }
 
   virtual void
   Send(JSContext* /*aCx*/, nsIDocument& aDoc, ErrorResult& aRv) override
   {
-    RequestBody<nsIDocument> body(&aDoc);
+    BodyExtractor<nsIDocument> body(&aDoc);
     aRv = SendInternal(&body);
   }
 
@@ -375,7 +349,7 @@ public:
     if (DOMStringIsNull(aString)) {
       Send(aCx, aRv);
     } else {
-      RequestBody<const nsAString> body(&aString);
+      BodyExtractor<const nsAString> body(&aString);
       aRv = SendInternal(&body);
     }
   }
@@ -383,7 +357,7 @@ public:
   virtual void
   Send(JSContext* /*aCx*/, FormData& aFormData, ErrorResult& aRv) override
   {
-    RequestBody<FormData> body(&aFormData);
+    BodyExtractor<nsIXHRSendable> body(&aFormData);
     aRv = SendInternal(&body);
   }
 
@@ -391,7 +365,7 @@ public:
   Send(JSContext* aCx, nsIInputStream* aStream, ErrorResult& aRv) override
   {
     NS_ASSERTION(aStream, "Null should go to string version");
-    RequestBody<nsIInputStream> body(aStream);
+    BodyExtractor<nsIInputStream> body(aStream);
     aRv = SendInternal(&body);
   }
 
diff --git a/dom/xhr/nsIXMLHttpRequest.idl b/dom/xhr/nsIXMLHttpRequest.idl
index 53e80bab70..5505bd47ee 100644
--- a/dom/xhr/nsIXMLHttpRequest.idl
+++ b/dom/xhr/nsIXMLHttpRequest.idl
@@ -326,9 +326,12 @@ interface nsIXMLHttpRequest : nsISupports
 
 [uuid(840d0d00-e83e-4a29-b3c7-67e96e90a499)]
 interface nsIXHRSendable : nsISupports {
+  // contentTypeWithCharset can be set to the contentType or
+  // contentType+charset based on what the spec says.
+  // See: https://fetch.spec.whatwg.org/#concept-bodyinit-extract
   void getSendInfo(out nsIInputStream body,
                    out uint64_t contentLength,
-                   out ACString contentType,
+                   out ACString contentTypeWithCharset,
                    out ACString charset);
 };