Add m-esr52 at 52.6.0

1 files changed, 1247 insertions, 0 deletions

diff --git a/dom/xbl/nsXBLBinding.cpp b/dom/xbl/nsXBLBinding.cpp
new file mode 100644
index 0000000000..6ae17c4c02
--- /dev/null
+++ b/dom/xbl/nsXBLBinding.cpp
@@ -0,0 +1,1247 @@
+/* -*- 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 "nsCOMPtr.h"
+#include "nsIAtom.h"
+#include "nsXBLDocumentInfo.h"
+#include "nsIInputStream.h"
+#include "nsNameSpaceManager.h"
+#include "nsIURI.h"
+#include "nsIURL.h"
+#include "nsIChannel.h"
+#include "nsXPIDLString.h"
+#include "nsReadableUtils.h"
+#include "plstr.h"
+#include "nsIContent.h"
+#include "nsIDocument.h"
+#include "nsContentUtils.h"
+#include "ChildIterator.h"
+#ifdef MOZ_XUL
+#include "nsIXULDocument.h"
+#endif
+#include "nsIXMLContentSink.h"
+#include "nsContentCID.h"
+#include "mozilla/dom/XMLDocument.h"
+#include "jsapi.h"
+#include "nsXBLService.h"
+#include "nsIXPConnect.h"
+#include "nsIScriptContext.h"
+#include "nsCRT.h"
+
+// Event listeners
+#include "mozilla/EventListenerManager.h"
+#include "nsIDOMEventListener.h"
+#include "nsAttrName.h"
+
+#include "nsGkAtoms.h"
+
+#include "nsXBLPrototypeHandler.h"
+
+#include "nsXBLPrototypeBinding.h"
+#include "nsXBLBinding.h"
+#include "nsIPrincipal.h"
+#include "nsIScriptSecurityManager.h"
+#include "mozilla/dom/XBLChildrenElement.h"
+
+#include "prprf.h"
+#include "nsNodeUtils.h"
+#include "nsJSUtils.h"
+
+// Nasty hack.  Maybe we could move some of the classinfo utility methods
+// (e.g. WrapNative) over to nsContentUtils?
+#include "nsDOMClassInfo.h"
+
+#include "mozilla/DeferredFinalize.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/ShadowRoot.h"
+#include "mozilla/ServoStyleSet.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// Helper classes
+
+/***********************************************************************/
+//
+// The JS class for XBLBinding
+//
+static void
+XBLFinalize(JSFreeOp *fop, JSObject *obj)
+{
+  nsXBLDocumentInfo* docInfo =
+    static_cast<nsXBLDocumentInfo*>(::JS_GetPrivate(obj));
+  DeferredFinalize(docInfo);
+}
+
+static bool
+XBLEnumerate(JSContext *cx, JS::Handle<JSObject*> obj)
+{
+  nsXBLPrototypeBinding* protoBinding =
+    static_cast<nsXBLPrototypeBinding*>(::JS_GetReservedSlot(obj, 0).toPrivate());
+  MOZ_ASSERT(protoBinding);
+
+  return protoBinding->ResolveAllFields(cx, obj);
+}
+
+static const JSClassOps gPrototypeJSClassOps = {
+    nullptr, nullptr, nullptr, nullptr,
+    XBLEnumerate, nullptr,
+    nullptr, XBLFinalize,
+    nullptr, nullptr, nullptr, nullptr
+};
+
+static const JSClass gPrototypeJSClass = {
+    "XBL prototype JSClass",
+    JSCLASS_HAS_PRIVATE |
+    JSCLASS_PRIVATE_IS_NSISUPPORTS |
+    JSCLASS_FOREGROUND_FINALIZE |
+    // Our one reserved slot holds the relevant nsXBLPrototypeBinding
+    JSCLASS_HAS_RESERVED_SLOTS(1),
+    &gPrototypeJSClassOps
+};
+
+// Implementation /////////////////////////////////////////////////////////////////
+
+// Constructors/Destructors
+nsXBLBinding::nsXBLBinding(nsXBLPrototypeBinding* aBinding)
+  : mMarkedForDeath(false)
+  , mUsingContentXBLScope(false)
+  , mIsShadowRootBinding(false)
+  , mPrototypeBinding(aBinding)
+{
+  NS_ASSERTION(mPrototypeBinding, "Must have a prototype binding!");
+  // Grab a ref to the document info so the prototype binding won't die
+  NS_ADDREF(mPrototypeBinding->XBLDocumentInfo());
+}
+
+// Constructor used by web components.
+nsXBLBinding::nsXBLBinding(ShadowRoot* aShadowRoot, nsXBLPrototypeBinding* aBinding)
+  : mMarkedForDeath(false),
+    mUsingContentXBLScope(false),
+    mIsShadowRootBinding(true),
+    mPrototypeBinding(aBinding),
+    mContent(aShadowRoot)
+{
+  NS_ASSERTION(mPrototypeBinding, "Must have a prototype binding!");
+  // Grab a ref to the document info so the prototype binding won't die
+  NS_ADDREF(mPrototypeBinding->XBLDocumentInfo());
+}
+
+nsXBLBinding::~nsXBLBinding(void)
+{
+  if (mContent && !mIsShadowRootBinding) {
+    // It is unnecessary to uninstall anonymous content in a shadow tree
+    // because the ShadowRoot itself is a DocumentFragment and does not
+    // need any additional cleanup.
+    nsXBLBinding::UninstallAnonymousContent(mContent->OwnerDoc(), mContent);
+  }
+  nsXBLDocumentInfo* info = mPrototypeBinding->XBLDocumentInfo();
+  NS_RELEASE(info);
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsXBLBinding)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsXBLBinding)
+  // XXX Probably can't unlink mPrototypeBinding->XBLDocumentInfo(), because
+  //     mPrototypeBinding is weak.
+  if (tmp->mContent && !tmp->mIsShadowRootBinding) {
+    nsXBLBinding::UninstallAnonymousContent(tmp->mContent->OwnerDoc(),
+                                            tmp->mContent);
+  }
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mContent)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mNextBinding)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mDefaultInsertionPoint)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mInsertionPoints)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mAnonymousContentList)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsXBLBinding)
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb,
+                                     "mPrototypeBinding->XBLDocumentInfo()");
+  cb.NoteXPCOMChild(tmp->mPrototypeBinding->XBLDocumentInfo());
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mContent)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mNextBinding)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDefaultInsertionPoint)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInsertionPoints)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAnonymousContentList)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(nsXBLBinding, AddRef)
+NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(nsXBLBinding, Release)
+
+void
+nsXBLBinding::SetBaseBinding(nsXBLBinding* aBinding)
+{
+  if (mNextBinding) {
+    NS_ERROR("Base XBL binding is already defined!");
+    return;
+  }
+
+  mNextBinding = aBinding; // Comptr handles rel/add
+}
+
+nsXBLBinding*
+nsXBLBinding::GetBindingWithContent()
+{
+  if (mContent) {
+    return this;
+  }
+
+  return mNextBinding ? mNextBinding->GetBindingWithContent() : nullptr;
+}
+
+void
+nsXBLBinding::InstallAnonymousContent(nsIContent* aAnonParent, nsIContent* aElement,
+                                      bool aChromeOnlyContent)
+{
+  // We need to ensure two things.
+  // (1) The anonymous content should be fooled into thinking it's in the bound
+  // element's document, assuming that the bound element is in a document
+  // Note that we don't change the current doc of aAnonParent here, since that
+  // quite simply does not matter.  aAnonParent is just a way of keeping refs
+  // to all its kids, which are anonymous content from the point of view of
+  // aElement.
+  // (2) The children's parent back pointer should not be to this synthetic root
+  // but should instead point to the enclosing parent element.
+  nsIDocument* doc = aElement->GetUncomposedDoc();
+  bool allowScripts = AllowScripts();
+
+  nsAutoScriptBlocker scriptBlocker;
+  for (nsIContent* child = aAnonParent->GetFirstChild();
+       child;
+       child = child->GetNextSibling()) {
+    child->UnbindFromTree();
+    if (aChromeOnlyContent) {
+      child->SetFlags(NODE_CHROME_ONLY_ACCESS |
+                      NODE_IS_ROOT_OF_CHROME_ONLY_ACCESS);
+    }
+    nsresult rv =
+      child->BindToTree(doc, aElement, mBoundElement, allowScripts);
+    if (NS_FAILED(rv)) {
+      // Oh, well... Just give up.
+      // XXXbz This really shouldn't be a void method!
+      child->UnbindFromTree();
+      return;
+    }
+
+    child->SetFlags(NODE_IS_ANONYMOUS_ROOT);
+
+#ifdef MOZ_XUL
+    // To make XUL templates work (and other goodies that happen when
+    // an element is added to a XUL document), we need to notify the
+    // XUL document using its special API.
+    nsCOMPtr<nsIXULDocument> xuldoc(do_QueryInterface(doc));
+    if (xuldoc)
+      xuldoc->AddSubtreeToDocument(child);
+#endif
+  }
+}
+
+void
+nsXBLBinding::UninstallAnonymousContent(nsIDocument* aDocument,
+                                        nsIContent* aAnonParent)
+{
+  nsAutoScriptBlocker scriptBlocker;
+  // Hold a strong ref while doing this, just in case.
+  nsCOMPtr<nsIContent> anonParent = aAnonParent;
+#ifdef MOZ_XUL
+  nsCOMPtr<nsIXULDocument> xuldoc =
+    do_QueryInterface(aDocument);
+#endif
+  for (nsIContent* child = aAnonParent->GetFirstChild();
+       child;
+       child = child->GetNextSibling()) {
+    child->UnbindFromTree();
+#ifdef MOZ_XUL
+    if (xuldoc) {
+      xuldoc->RemoveSubtreeFromDocument(child);
+    }
+#endif
+  }
+}
+
+void
+nsXBLBinding::SetBoundElement(nsIContent* aElement)
+{
+  mBoundElement = aElement;
+  if (mNextBinding)
+    mNextBinding->SetBoundElement(aElement);
+
+  if (!mBoundElement) {
+    return;
+  }
+
+  // Compute whether we're using an XBL scope.
+  //
+  // We disable XBL scopes for remote XUL, where we care about compat more
+  // than security. So we need to know whether we're using an XBL scope so that
+  // we can decide what to do about untrusted events when "allowuntrusted"
+  // is not given in the handler declaration.
+  nsCOMPtr<nsIGlobalObject> go = mBoundElement->OwnerDoc()->GetScopeObject();
+  NS_ENSURE_TRUE_VOID(go && go->GetGlobalJSObject());
+  mUsingContentXBLScope = xpc::UseContentXBLScope(js::GetObjectCompartment(go->GetGlobalJSObject()));
+}
+
+bool
+nsXBLBinding::HasStyleSheets() const
+{
+  // Find out if we need to re-resolve style.  We'll need to do this
+  // if we have additional stylesheets in our binding document.
+  if (mPrototypeBinding->HasStyleSheets())
+    return true;
+
+  return mNextBinding ? mNextBinding->HasStyleSheets() : false;
+}
+
+void
+nsXBLBinding::GenerateAnonymousContent()
+{
+  NS_ASSERTION(!nsContentUtils::IsSafeToRunScript(),
+               "Someone forgot a script blocker");
+
+  // Fetch the content element for this binding.
+  nsIContent* content =
+    mPrototypeBinding->GetImmediateChild(nsGkAtoms::content);
+
+  if (!content) {
+    // We have no anonymous content.
+    if (mNextBinding)
+      mNextBinding->GenerateAnonymousContent();
+
+    return;
+  }
+
+  // Find out if we're really building kids or if we're just
+  // using the attribute-setting shorthand hack.
+  uint32_t contentCount = content->GetChildCount();
+
+  // Plan to build the content by default.
+  bool hasContent = (contentCount > 0);
+  if (hasContent) {
+    nsIDocument* doc = mBoundElement->OwnerDoc();
+
+    nsCOMPtr<nsINode> clonedNode;
+    nsCOMArray<nsINode> nodesWithProperties;
+    nsNodeUtils::Clone(content, true, doc->NodeInfoManager(),
+                       nodesWithProperties, getter_AddRefs(clonedNode));
+    mContent = clonedNode->AsElement();
+
+    // Search for <xbl:children> elements in the XBL content. In the presence
+    // of multiple default insertion points, we use the last one in document
+    // order.
+    for (nsIContent* child = mContent; child; child = child->GetNextNode(mContent)) {
+      if (child->NodeInfo()->Equals(nsGkAtoms::children, kNameSpaceID_XBL)) {
+        XBLChildrenElement* point = static_cast<XBLChildrenElement*>(child);
+        if (point->IsDefaultInsertion()) {
+          mDefaultInsertionPoint = point;
+        } else {
+          mInsertionPoints.AppendElement(point);
+        }
+      }
+    }
+
+    // Do this after looking for <children> as this messes up the parent
+    // pointer which would make the GetNextNode call above fail
+    InstallAnonymousContent(mContent, mBoundElement,
+                            mPrototypeBinding->ChromeOnlyContent());
+
+    // Insert explicit children into insertion points
+    if (mDefaultInsertionPoint && mInsertionPoints.IsEmpty()) {
+      ExplicitChildIterator iter(mBoundElement);
+      for (nsIContent* child = iter.GetNextChild(); child; child = iter.GetNextChild()) {
+        mDefaultInsertionPoint->AppendInsertedChild(child);
+      }
+    } else {
+      // It is odd to come into this code if mInsertionPoints is not empty, but
+      // we need to make sure to do the compatibility hack below if the bound
+      // node has any non <xul:template> or <xul:observes> children.
+      ExplicitChildIterator iter(mBoundElement);
+      for (nsIContent* child = iter.GetNextChild(); child; child = iter.GetNextChild()) {
+        XBLChildrenElement* point = FindInsertionPointForInternal(child);
+        if (point) {
+          point->AppendInsertedChild(child);
+        } else {
+          NodeInfo *ni = child->NodeInfo();
+          if (ni->NamespaceID() != kNameSpaceID_XUL ||
+              (!ni->Equals(nsGkAtoms::_template) &&
+               !ni->Equals(nsGkAtoms::observes))) {
+            // Compatibility hack. For some reason the original XBL
+            // implementation dropped the content of a binding if any child of
+            // the bound element didn't match any of the <children> in the
+            // binding. This became a pseudo-API that we have to maintain.
+
+            // Undo InstallAnonymousContent
+            UninstallAnonymousContent(doc, mContent);
+
+            // Clear out our children elements to avoid dangling references.
+            ClearInsertionPoints();
+
+            // Pretend as though there was no content in the binding.
+            mContent = nullptr;
+            return;
+          }
+        }
+      }
+    }
+
+    // Set binding parent on default content if need
+    if (mDefaultInsertionPoint) {
+      mDefaultInsertionPoint->MaybeSetupDefaultContent();
+    }
+    for (uint32_t i = 0; i < mInsertionPoints.Length(); ++i) {
+      mInsertionPoints[i]->MaybeSetupDefaultContent();
+    }
+
+    mPrototypeBinding->SetInitialAttributes(mBoundElement, mContent);
+  }
+
+  // Always check the content element for potential attributes.
+  // This shorthand hack always happens, even when we didn't
+  // build anonymous content.
+  BorrowedAttrInfo attrInfo;
+  for (uint32_t i = 0; (attrInfo = content->GetAttrInfoAt(i)); ++i) {
+    int32_t namespaceID = attrInfo.mName->NamespaceID();
+    // Hold a strong reference here so that the atom doesn't go away during
+    // UnsetAttr.
+    nsCOMPtr<nsIAtom> name = attrInfo.mName->LocalName();
+
+    if (name != nsGkAtoms::includes) {
+      if (!nsContentUtils::HasNonEmptyAttr(mBoundElement, namespaceID, name)) {
+        nsAutoString value2;
+        attrInfo.mValue->ToString(value2);
+        mBoundElement->SetAttr(namespaceID, name, attrInfo.mName->GetPrefix(),
+                               value2, false);
+      }
+    }
+
+    // Conserve space by wiping the attributes off the clone.
+    if (mContent)
+      mContent->UnsetAttr(namespaceID, name, false);
+  }
+
+  // Now that we've finished shuffling the tree around, go ahead and restyle it
+  // since frame construction is about to happen.
+  nsIPresShell* presShell = mBoundElement->OwnerDoc()->GetShell();
+  ServoStyleSet* servoSet = presShell->StyleSet()->GetAsServo();
+  if (servoSet) {
+    mBoundElement->SetHasDirtyDescendantsForServo();
+    servoSet->StyleNewChildren(mBoundElement);
+  }
+}
+
+nsIURI*
+nsXBLBinding::GetSourceDocURI()
+{
+  nsIContent* targetContent =
+    mPrototypeBinding->GetImmediateChild(nsGkAtoms::content);
+  if (!targetContent) {
+    return nullptr;
+  }
+
+  return targetContent->OwnerDoc()->GetDocumentURI();
+}
+
+XBLChildrenElement*
+nsXBLBinding::FindInsertionPointFor(nsIContent* aChild)
+{
+  // XXX We should get rid of this function as it causes us to traverse the
+  // binding chain multiple times
+  if (mContent) {
+    return FindInsertionPointForInternal(aChild);
+  }
+
+  return mNextBinding ? mNextBinding->FindInsertionPointFor(aChild)
+                      : nullptr;
+}
+
+XBLChildrenElement*
+nsXBLBinding::FindInsertionPointForInternal(nsIContent* aChild)
+{
+  for (uint32_t i = 0; i < mInsertionPoints.Length(); ++i) {
+    XBLChildrenElement* point = mInsertionPoints[i];
+    if (point->Includes(aChild)) {
+      return point;
+    }
+  }
+
+  return mDefaultInsertionPoint;
+}
+
+void
+nsXBLBinding::ClearInsertionPoints()
+{
+  if (mDefaultInsertionPoint) {
+    mDefaultInsertionPoint->ClearInsertedChildren();
+  }
+
+  for (uint32_t i = 0; i < mInsertionPoints.Length(); ++i) {
+    mInsertionPoints[i]->ClearInsertedChildren();
+  }
+}
+
+nsAnonymousContentList*
+nsXBLBinding::GetAnonymousNodeList()
+{
+  if (!mContent) {
+    return mNextBinding ? mNextBinding->GetAnonymousNodeList() : nullptr;
+  }
+
+  if (!mAnonymousContentList) {
+    mAnonymousContentList = new nsAnonymousContentList(mContent);
+  }
+
+  return mAnonymousContentList;
+}
+
+void
+nsXBLBinding::InstallEventHandlers()
+{
+  // Don't install handlers if scripts aren't allowed.
+  if (AllowScripts()) {
+    // Fetch the handlers prototypes for this binding.
+    nsXBLPrototypeHandler* handlerChain = mPrototypeBinding->GetPrototypeHandlers();
+
+    if (handlerChain) {
+      EventListenerManager* manager = mBoundElement->GetOrCreateListenerManager();
+      if (!manager)
+        return;
+
+      bool isChromeDoc =
+        nsContentUtils::IsChromeDoc(mBoundElement->OwnerDoc());
+      bool isChromeBinding = mPrototypeBinding->IsChrome();
+      nsXBLPrototypeHandler* curr;
+      for (curr = handlerChain; curr; curr = curr->GetNextHandler()) {
+        // Fetch the event type.
+        nsCOMPtr<nsIAtom> eventAtom = curr->GetEventName();
+        if (!eventAtom ||
+            eventAtom == nsGkAtoms::keyup ||
+            eventAtom == nsGkAtoms::keydown ||
+            eventAtom == nsGkAtoms::keypress)
+          continue;
+
+        nsXBLEventHandler* handler = curr->GetEventHandler();
+        if (handler) {
+          // Figure out if we're using capturing or not.
+          EventListenerFlags flags;
+          flags.mCapture = (curr->GetPhase() == NS_PHASE_CAPTURING);
+
+          // If this is a command, add it in the system event group
+          if ((curr->GetType() & (NS_HANDLER_TYPE_XBL_COMMAND |
+                                  NS_HANDLER_TYPE_SYSTEM)) &&
+              (isChromeBinding || mBoundElement->IsInNativeAnonymousSubtree())) {
+            flags.mInSystemGroup = true;
+          }
+
+          bool hasAllowUntrustedAttr = curr->HasAllowUntrustedAttr();
+          if ((hasAllowUntrustedAttr && curr->AllowUntrustedEvents()) ||
+              (!hasAllowUntrustedAttr && !isChromeDoc && !mUsingContentXBLScope)) {
+            flags.mAllowUntrustedEvents = true;
+          }
+
+          manager->AddEventListenerByType(handler,
+                                          nsDependentAtomString(eventAtom),
+                                          flags);
+        }
+      }
+
+      const nsCOMArray<nsXBLKeyEventHandler>* keyHandlers =
+        mPrototypeBinding->GetKeyEventHandlers();
+      int32_t i;
+      for (i = 0; i < keyHandlers->Count(); ++i) {
+        nsXBLKeyEventHandler* handler = keyHandlers->ObjectAt(i);
+        handler->SetIsBoundToChrome(isChromeDoc);
+        handler->SetUsingContentXBLScope(mUsingContentXBLScope);
+
+        nsAutoString type;
+        handler->GetEventName(type);
+
+        // If this is a command, add it in the system event group, otherwise
+        // add it to the standard event group.
+
+        // Figure out if we're using capturing or not.
+        EventListenerFlags flags;
+        flags.mCapture = (handler->GetPhase() == NS_PHASE_CAPTURING);
+
+        if ((handler->GetType() & (NS_HANDLER_TYPE_XBL_COMMAND |
+                                   NS_HANDLER_TYPE_SYSTEM)) &&
+            (isChromeBinding || mBoundElement->IsInNativeAnonymousSubtree())) {
+          flags.mInSystemGroup = true;
+        }
+
+        // For key handlers we have to set mAllowUntrustedEvents flag.
+        // Whether the handling of the event is allowed or not is handled in
+        // nsXBLKeyEventHandler::HandleEvent
+        flags.mAllowUntrustedEvents = true;
+
+        manager->AddEventListenerByType(handler, type, flags);
+      }
+    }
+  }
+
+  if (mNextBinding)
+    mNextBinding->InstallEventHandlers();
+}
+
+nsresult
+nsXBLBinding::InstallImplementation()
+{
+  // Always install the base class properties first, so that
+  // derived classes can reference the base class properties.
+
+  if (mNextBinding) {
+    nsresult rv = mNextBinding->InstallImplementation();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // iterate through each property in the prototype's list and install the property.
+  if (AllowScripts())
+    return mPrototypeBinding->InstallImplementation(this);
+
+  return NS_OK;
+}
+
+nsIAtom*
+nsXBLBinding::GetBaseTag(int32_t* aNameSpaceID)
+{
+  nsIAtom *tag = mPrototypeBinding->GetBaseTag(aNameSpaceID);
+  if (!tag && mNextBinding)
+    return mNextBinding->GetBaseTag(aNameSpaceID);
+
+  return tag;
+}
+
+void
+nsXBLBinding::AttributeChanged(nsIAtom* aAttribute, int32_t aNameSpaceID,
+                               bool aRemoveFlag, bool aNotify)
+{
+  // XXX Change if we ever allow multiple bindings in a chain to contribute anonymous content
+  if (!mContent) {
+    if (mNextBinding)
+      mNextBinding->AttributeChanged(aAttribute, aNameSpaceID,
+                                     aRemoveFlag, aNotify);
+  } else {
+    mPrototypeBinding->AttributeChanged(aAttribute, aNameSpaceID, aRemoveFlag,
+                                        mBoundElement, mContent, aNotify);
+  }
+}
+
+void
+nsXBLBinding::ExecuteAttachedHandler()
+{
+  if (mNextBinding)
+    mNextBinding->ExecuteAttachedHandler();
+
+  if (AllowScripts())
+    mPrototypeBinding->BindingAttached(mBoundElement);
+}
+
+void
+nsXBLBinding::ExecuteDetachedHandler()
+{
+  if (AllowScripts())
+    mPrototypeBinding->BindingDetached(mBoundElement);
+
+  if (mNextBinding)
+    mNextBinding->ExecuteDetachedHandler();
+}
+
+void
+nsXBLBinding::UnhookEventHandlers()
+{
+  nsXBLPrototypeHandler* handlerChain = mPrototypeBinding->GetPrototypeHandlers();
+
+  if (handlerChain) {
+    EventListenerManager* manager = mBoundElement->GetExistingListenerManager();
+    if (!manager) {
+      return;
+    }
+
+    bool isChromeBinding = mPrototypeBinding->IsChrome();
+    nsXBLPrototypeHandler* curr;
+    for (curr = handlerChain; curr; curr = curr->GetNextHandler()) {
+      nsXBLEventHandler* handler = curr->GetCachedEventHandler();
+      if (!handler) {
+        continue;
+      }
+
+      nsCOMPtr<nsIAtom> eventAtom = curr->GetEventName();
+      if (!eventAtom ||
+          eventAtom == nsGkAtoms::keyup ||
+          eventAtom == nsGkAtoms::keydown ||
+          eventAtom == nsGkAtoms::keypress)
+        continue;
+
+      // Figure out if we're using capturing or not.
+      EventListenerFlags flags;
+      flags.mCapture = (curr->GetPhase() == NS_PHASE_CAPTURING);
+
+      // If this is a command, remove it from the system event group,
+      // otherwise remove it from the standard event group.
+
+      if ((curr->GetType() & (NS_HANDLER_TYPE_XBL_COMMAND |
+                              NS_HANDLER_TYPE_SYSTEM)) &&
+          (isChromeBinding || mBoundElement->IsInNativeAnonymousSubtree())) {
+        flags.mInSystemGroup = true;
+      }
+
+      manager->RemoveEventListenerByType(handler,
+                                         nsDependentAtomString(eventAtom),
+                                         flags);
+    }
+
+    const nsCOMArray<nsXBLKeyEventHandler>* keyHandlers =
+      mPrototypeBinding->GetKeyEventHandlers();
+    int32_t i;
+    for (i = 0; i < keyHandlers->Count(); ++i) {
+      nsXBLKeyEventHandler* handler = keyHandlers->ObjectAt(i);
+
+      nsAutoString type;
+      handler->GetEventName(type);
+
+      // Figure out if we're using capturing or not.
+      EventListenerFlags flags;
+      flags.mCapture = (handler->GetPhase() == NS_PHASE_CAPTURING);
+
+      // If this is a command, remove it from the system event group, otherwise
+      // remove it from the standard event group.
+
+      if ((handler->GetType() & (NS_HANDLER_TYPE_XBL_COMMAND | NS_HANDLER_TYPE_SYSTEM)) &&
+          (isChromeBinding || mBoundElement->IsInNativeAnonymousSubtree())) {
+        flags.mInSystemGroup = true;
+      }
+
+      manager->RemoveEventListenerByType(handler, type, flags);
+    }
+  }
+}
+
+static void
+UpdateInsertionParent(XBLChildrenElement* aPoint,
+                      nsIContent* aOldBoundElement)
+{
+  if (aPoint->IsDefaultInsertion()) {
+    return;
+  }
+
+  for (size_t i = 0; i < aPoint->InsertedChildrenLength(); ++i) {
+    nsIContent* child = aPoint->InsertedChild(i);
+
+    MOZ_ASSERT(child->GetParentNode());
+
+    // Here, we're iterating children that we inserted. There are two cases:
+    // either |child| is an explicit child of |aOldBoundElement| and is no
+    // longer inserted anywhere or it's a child of a <children> element
+    // parented to |aOldBoundElement|. In the former case, the child is no
+    // longer inserted anywhere, so we set its insertion parent to null. In the
+    // latter case, the child is now inserted into |aOldBoundElement| from some
+    // binding above us, so we set its insertion parent to aOldBoundElement.
+    if (child->GetParentNode() == aOldBoundElement) {
+      child->SetXBLInsertionParent(nullptr);
+    } else {
+      child->SetXBLInsertionParent(aOldBoundElement);
+    }
+  }
+}
+
+void
+nsXBLBinding::ChangeDocument(nsIDocument* aOldDocument, nsIDocument* aNewDocument)
+{
+  if (aOldDocument == aNewDocument)
+    return;
+
+  // Now the binding dies.  Unhook our prototypes.
+  if (mPrototypeBinding->HasImplementation()) {
+    AutoJSAPI jsapi;
+    // Init might fail here if we've cycle-collected the global object, since
+    // the Unlink phase of cycle collection happens after JS GC finalization.
+    // But in that case, we don't care about fixing the prototype chain, since
+    // everything's going away immediately.
+    if (jsapi.Init(aOldDocument->GetScopeObject())) {
+      JSContext* cx = jsapi.cx();
+
+      JS::Rooted<JSObject*> scriptObject(cx, mBoundElement->GetWrapper());
+      if (scriptObject) {
+        // XXX Stay in sync! What if a layered binding has an
+        // <interface>?!
+        // XXXbz what does that comment mean, really?  It seems to date
+        // back to when there was such a thing as an <interface>, whever
+        // that was...
+
+        // Find the right prototype.
+        JSAutoCompartment ac(cx, scriptObject);
+
+        JS::Rooted<JSObject*> base(cx, scriptObject);
+        JS::Rooted<JSObject*> proto(cx);
+        for ( ; true; base = proto) { // Will break out on null proto
+          if (!JS_GetPrototype(cx, base, &proto)) {
+            return;
+          }
+          if (!proto) {
+            break;
+          }
+
+          if (JS_GetClass(proto) != &gPrototypeJSClass) {
+            // Clearly not the right class
+            continue;
+          }
+
+          RefPtr<nsXBLDocumentInfo> docInfo =
+            static_cast<nsXBLDocumentInfo*>(::JS_GetPrivate(proto));
+          if (!docInfo) {
+            // Not the proto we seek
+            continue;
+          }
+
+          JS::Value protoBinding = ::JS_GetReservedSlot(proto, 0);
+
+          if (protoBinding.toPrivate() != mPrototypeBinding) {
+            // Not the right binding
+            continue;
+          }
+
+          // Alright!  This is the right prototype.  Pull it out of the
+          // proto chain.
+          JS::Rooted<JSObject*> grandProto(cx);
+          if (!JS_GetPrototype(cx, proto, &grandProto)) {
+            return;
+          }
+          ::JS_SetPrototype(cx, base, grandProto);
+          break;
+        }
+
+        mPrototypeBinding->UndefineFields(cx, scriptObject);
+
+        // Don't remove the reference from the document to the
+        // wrapper here since it'll be removed by the element
+        // itself when that's taken out of the document.
+      }
+    }
+  }
+
+  // Remove our event handlers
+  UnhookEventHandlers();
+
+  {
+    nsAutoScriptBlocker scriptBlocker;
+
+    // Then do our ancestors.  This reverses the construction order, so that at
+    // all times things are consistent as far as everyone is concerned.
+    if (mNextBinding) {
+      mNextBinding->ChangeDocument(aOldDocument, aNewDocument);
+    }
+
+    // Update the anonymous content.
+    // XXXbz why not only for style bindings?
+    if (mContent && !mIsShadowRootBinding) {
+      nsXBLBinding::UninstallAnonymousContent(aOldDocument, mContent);
+    }
+
+    // Now that we've unbound our anonymous content from the tree and updated
+    // its binding parent, update the insertion parent for content inserted
+    // into our <children> elements.
+    if (mDefaultInsertionPoint) {
+      UpdateInsertionParent(mDefaultInsertionPoint, mBoundElement);
+    }
+
+    for (size_t i = 0; i < mInsertionPoints.Length(); ++i) {
+      UpdateInsertionParent(mInsertionPoints[i], mBoundElement);
+    }
+
+    // Now that our inserted children no longer think they're inserted
+    // anywhere, make sure our internal state reflects that as well.
+    ClearInsertionPoints();
+  }
+}
+
+bool
+nsXBLBinding::InheritsStyle() const
+{
+  // XXX Will have to change if we ever allow multiple bindings to contribute anonymous content.
+  // Most derived binding with anonymous content determines style inheritance for now.
+
+  // XXX What about bindings with <content> but no kids, e.g., my treecell-text binding?
+  if (mContent)
+    return mPrototypeBinding->InheritsStyle();
+
+  if (mNextBinding)
+    return mNextBinding->InheritsStyle();
+
+  return true;
+}
+
+void
+nsXBLBinding::WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc, void* aData)
+{
+  if (mNextBinding)
+    mNextBinding->WalkRules(aFunc, aData);
+
+  nsIStyleRuleProcessor *rules = mPrototypeBinding->GetRuleProcessor();
+  if (rules)
+    (*aFunc)(rules, aData);
+}
+
+// Internal helper methods ////////////////////////////////////////////////////////////////
+
+// Get or create a WeakMap object on a given XBL-hosting global.
+//
+// The scheme is as follows. XBL-hosting globals (either privileged content
+// Windows or XBL scopes) get two lazily-defined WeakMap properties. Each
+// WeakMap is keyed by the grand-proto - i.e. the original prototype of the
+// content before it was bound, and the prototype of the class object that we
+// splice in. The values in the WeakMap are simple dictionary-style objects,
+// mapping from XBL class names to class objects.
+static JSObject*
+GetOrCreateClassObjectMap(JSContext *cx, JS::Handle<JSObject*> scope, const char *mapName)
+{
+  AssertSameCompartment(cx, scope);
+  MOZ_ASSERT(JS_IsGlobalObject(scope));
+  MOZ_ASSERT(scope == xpc::GetXBLScopeOrGlobal(cx, scope));
+
+  // First, see if the map is already defined.
+  JS::Rooted<JS::PropertyDescriptor> desc(cx);
+  if (!JS_GetOwnPropertyDescriptor(cx, scope, mapName, &desc)) {
+    return nullptr;
+  }
+  if (desc.object() && desc.value().isObject() &&
+      JS::IsWeakMapObject(&desc.value().toObject())) {
+    return &desc.value().toObject();
+  }
+
+  // It's not there. Create and define it.
+  JS::Rooted<JSObject*> map(cx, JS::NewWeakMapObject(cx));
+  if (!map || !JS_DefineProperty(cx, scope, mapName, map,
+                                 JSPROP_PERMANENT | JSPROP_READONLY,
+                                 JS_STUBGETTER, JS_STUBSETTER))
+  {
+    return nullptr;
+  }
+  return map;
+}
+
+static JSObject*
+GetOrCreateMapEntryForPrototype(JSContext *cx, JS::Handle<JSObject*> proto)
+{
+  AssertSameCompartment(cx, proto);
+  // We want to hang our class objects off the XBL scope. But since we also
+  // hoist anonymous content into the XBL scope, this creates the potential for
+  // tricky collisions, since we can simultaneously  have a bound in-content
+  // node with grand-proto HTMLDivElement and a bound anonymous node whose
+  // grand-proto is the XBL scope's cross-compartment wrapper to HTMLDivElement.
+  // Since we have to wrap the WeakMap keys into its scope, this distinction
+  // would be lost if we don't do something about it.
+  //
+  // So we define two maps - one class objects that live in content (prototyped
+  // to content prototypes), and the other for class objects that live in the
+  // XBL scope (prototyped to cross-compartment-wrapped content prototypes).
+  const char* name = xpc::IsInContentXBLScope(proto) ? "__ContentClassObjectMap__"
+                                                     : "__XBLClassObjectMap__";
+
+  // Now, enter the XBL scope, since that's where we need to operate, and wrap
+  // the proto accordingly. We hang the map off of the content XBL scope for
+  // content, and the Window for chrome (whether add-ons are involved or not).
+  JS::Rooted<JSObject*> scope(cx, xpc::GetXBLScopeOrGlobal(cx, proto));
+  NS_ENSURE_TRUE(scope, nullptr);
+  MOZ_ASSERT(js::GetGlobalForObjectCrossCompartment(scope) == scope);
+
+  JS::Rooted<JSObject*> wrappedProto(cx, proto);
+  JSAutoCompartment ac(cx, scope);
+  if (!JS_WrapObject(cx, &wrappedProto)) {
+    return nullptr;
+  }
+
+  // Grab the appropriate WeakMap.
+  JS::Rooted<JSObject*> map(cx, GetOrCreateClassObjectMap(cx, scope, name));
+  if (!map) {
+    return nullptr;
+  }
+
+  // See if we already have a map entry for that prototype.
+  JS::Rooted<JS::Value> val(cx);
+  if (!JS::GetWeakMapEntry(cx, map, wrappedProto, &val)) {
+    return nullptr;
+  }
+  if (val.isObject()) {
+    return &val.toObject();
+  }
+
+  // We don't have an entry. Create one and stick it in the map.
+  JS::Rooted<JSObject*> entry(cx);
+  entry = JS_NewObjectWithGivenProto(cx, nullptr, nullptr);
+  if (!entry) {
+    return nullptr;
+  }
+  JS::Rooted<JS::Value> entryVal(cx, JS::ObjectValue(*entry));
+  if (!JS::SetWeakMapEntry(cx, map, wrappedProto, entryVal)) {
+    NS_WARNING("SetWeakMapEntry failed, probably due to non-preservable WeakMap "
+               "key. XBL binding will fail for this element.");
+    return nullptr;
+  }
+  return entry;
+}
+
+static
+nsXBLPrototypeBinding*
+GetProtoBindingFromClassObject(JSObject* obj)
+{
+  MOZ_ASSERT(JS_GetClass(obj) == &gPrototypeJSClass);
+  return static_cast<nsXBLPrototypeBinding*>(::JS_GetReservedSlot(obj, 0).toPrivate());
+}
+
+
+// static
+nsresult
+nsXBLBinding::DoInitJSClass(JSContext *cx,
+                            JS::Handle<JSObject*> obj,
+                            const nsAFlatString& aClassName,
+                            nsXBLPrototypeBinding* aProtoBinding,
+                            JS::MutableHandle<JSObject*> aClassObject,
+                            bool* aNew)
+{
+  MOZ_ASSERT(obj);
+
+  // Note that, now that NAC reflectors are created in the XBL scope, the
+  // reflector is not necessarily same-compartment with the document. So we'll
+  // end up creating a separate instance of the oddly-named XBL class object
+  // and defining it as a property on the XBL scope's global. This works fine,
+  // but we need to make sure never to assume that the the reflector and
+  // prototype are same-compartment with the bound document.
+  JS::Rooted<JSObject*> global(cx, js::GetGlobalForObjectCrossCompartment(obj));
+
+  // We never store class objects in add-on scopes.
+  JS::Rooted<JSObject*> xblScope(cx, xpc::GetXBLScopeOrGlobal(cx, global));
+  NS_ENSURE_TRUE(xblScope, NS_ERROR_UNEXPECTED);
+
+  JS::Rooted<JSObject*> parent_proto(cx);
+  if (!JS_GetPrototype(cx, obj, &parent_proto)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Get the map entry for the parent prototype. In the one-off case that the
+  // parent prototype is null, we somewhat hackily just use the WeakMap itself
+  // as a property holder.
+  JS::Rooted<JSObject*> holder(cx);
+  if (parent_proto) {
+    holder = GetOrCreateMapEntryForPrototype(cx, parent_proto);
+  } else {
+    JSAutoCompartment innerAC(cx, xblScope);
+    holder = GetOrCreateClassObjectMap(cx, xblScope, "__ContentClassObjectMap__");
+  }
+  if (NS_WARN_IF(!holder)) {
+    return NS_ERROR_FAILURE;
+  }
+  js::AssertSameCompartment(holder, xblScope);
+  JSAutoCompartment ac(cx, holder);
+
+  // Look up the class on the property holder. The only properties on the
+  // holder should be class objects. If we don't find the class object, we need
+  // to create and define it.
+  JS::Rooted<JSObject*> proto(cx);
+  JS::Rooted<JS::PropertyDescriptor> desc(cx);
+  if (!JS_GetOwnUCPropertyDescriptor(cx, holder, aClassName.get(), &desc)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  *aNew = !desc.object();
+  if (desc.object()) {
+    proto = &desc.value().toObject();
+    DebugOnly<nsXBLPrototypeBinding*> cachedBinding =
+      GetProtoBindingFromClassObject(js::UncheckedUnwrap(proto));
+    MOZ_ASSERT(cachedBinding == aProtoBinding);
+  } else {
+
+    // We need to create the prototype. First, enter the compartment where it's
+    // going to live, and create it.
+    JSAutoCompartment ac2(cx, global);
+    proto = JS_NewObjectWithGivenProto(cx, &gPrototypeJSClass, parent_proto);
+    if (!proto) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    // Keep this proto binding alive while we're alive.  Do this first so that
+    // we can guarantee that in XBLFinalize this will be non-null.
+    // Note that we can't just store aProtoBinding in the private and
+    // addref/release the nsXBLDocumentInfo through it, because cycle
+    // collection doesn't seem to work right if the private is not an
+    // nsISupports.
+    nsXBLDocumentInfo* docInfo = aProtoBinding->XBLDocumentInfo();
+    ::JS_SetPrivate(proto, docInfo);
+    NS_ADDREF(docInfo);
+    JS_SetReservedSlot(proto, 0, JS::PrivateValue(aProtoBinding));
+
+    // Next, enter the compartment of the property holder, wrap the proto, and
+    // stick it on.
+    JSAutoCompartment ac3(cx, holder);
+    if (!JS_WrapObject(cx, &proto) ||
+        !JS_DefineUCProperty(cx, holder, aClassName.get(), -1, proto,
+                             JSPROP_READONLY | JSPROP_PERMANENT,
+                             JS_STUBGETTER, JS_STUBSETTER))
+    {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+
+  // Whew. We have the proto. Wrap it back into the compartment of |obj|,
+  // splice it in, and return it.
+  JSAutoCompartment ac4(cx, obj);
+  if (!JS_WrapObject(cx, &proto) || !JS_SetPrototype(cx, obj, proto)) {
+    return NS_ERROR_FAILURE;
+  }
+  aClassObject.set(proto);
+  return NS_OK;
+}
+
+bool
+nsXBLBinding::AllowScripts()
+{
+  return mBoundElement && mPrototypeBinding->GetAllowScripts();
+}
+
+nsXBLBinding*
+nsXBLBinding::RootBinding()
+{
+  if (mNextBinding)
+    return mNextBinding->RootBinding();
+
+  return this;
+}
+
+bool
+nsXBLBinding::ResolveAllFields(JSContext *cx, JS::Handle<JSObject*> obj) const
+{
+  if (!mPrototypeBinding->ResolveAllFields(cx, obj)) {
+    return false;
+  }
+
+  if (mNextBinding) {
+    return mNextBinding->ResolveAllFields(cx, obj);
+  }
+
+  return true;
+}
+
+bool
+nsXBLBinding::LookupMember(JSContext* aCx, JS::Handle<jsid> aId,
+                           JS::MutableHandle<JS::PropertyDescriptor> aDesc)
+{
+  // We should never enter this function with a pre-filled property descriptor.
+  MOZ_ASSERT(!aDesc.object());
+
+  // Get the string as an nsString before doing anything, so we can make
+  // convenient comparisons during our search.
+  if (!JSID_IS_STRING(aId)) {
+    return true;
+  }
+  nsAutoJSString name;
+  if (!name.init(aCx, JSID_TO_STRING(aId))) {
+    return false;
+  }
+
+  // We have a weak reference to our bound element, so make sure it's alive.
+  if (!mBoundElement || !mBoundElement->GetWrapper()) {
+    return false;
+  }
+
+  // Get the scope of mBoundElement and the associated XBL scope. We should only
+  // be calling into this machinery if we're running in a separate XBL scope.
+  //
+  // Note that we only end up in LookupMember for XrayWrappers from XBL scopes
+  // into content. So for NAC reflectors that live in the XBL scope, we should
+  // never get here. But on the off-chance that someone adds new callsites to
+  // LookupMember, we do a release-mode assertion as belt-and-braces.
+  // We do a release-mode assertion here to be extra safe.
+  //
+  // This code is only called for content XBL, so we don't have to worry about
+  // add-on scopes here.
+  JS::Rooted<JSObject*> boundScope(aCx,
+    js::GetGlobalForObjectCrossCompartment(mBoundElement->GetWrapper()));
+  MOZ_RELEASE_ASSERT(!xpc::IsInAddonScope(boundScope));
+  MOZ_RELEASE_ASSERT(!xpc::IsInContentXBLScope(boundScope));
+  JS::Rooted<JSObject*> xblScope(aCx, xpc::GetXBLScope(aCx, boundScope));
+  NS_ENSURE_TRUE(xblScope, false);
+  MOZ_ASSERT(boundScope != xblScope);
+
+  // Enter the xbl scope and invoke the internal version.
+  {
+    JSAutoCompartment ac(aCx, xblScope);
+    JS::Rooted<jsid> id(aCx, aId);
+    if (!LookupMemberInternal(aCx, name, id, aDesc, xblScope)) {
+      return false;
+    }
+  }
+
+  // Wrap into the caller's scope.
+  return JS_WrapPropertyDescriptor(aCx, aDesc);
+}
+
+bool
+nsXBLBinding::LookupMemberInternal(JSContext* aCx, nsString& aName,
+                                   JS::Handle<jsid> aNameAsId,
+                                   JS::MutableHandle<JS::PropertyDescriptor> aDesc,
+                                   JS::Handle<JSObject*> aXBLScope)
+{
+  // First, see if we have an implementation. If we don't, it means that this
+  // binding doesn't have a class object, and thus doesn't have any members.
+  // Skip it.
+  if (!PrototypeBinding()->HasImplementation()) {
+    if (!mNextBinding) {
+      return true;
+    }
+    return mNextBinding->LookupMemberInternal(aCx, aName, aNameAsId,
+                                              aDesc, aXBLScope);
+  }
+
+  // Find our class object. It's in a protected scope and permanent just in case,
+  // so should be there no matter what.
+  JS::Rooted<JS::Value> classObject(aCx);
+  if (!JS_GetUCProperty(aCx, aXBLScope, PrototypeBinding()->ClassName().get(),
+                        -1, &classObject)) {
+    return false;
+  }
+
+  // The bound element may have been adoped by a document and have a different
+  // wrapper (and different xbl scope) than when the binding was applied, in
+  // this case getting the class object will fail. Behave as if the class
+  // object did not exist.
+  if (classObject.isUndefined()) {
+    return true;
+  }
+
+  MOZ_ASSERT(classObject.isObject());
+
+  // Look for the property on this binding. If it's not there, try the next
+  // binding on the chain.
+  nsXBLProtoImpl* impl = mPrototypeBinding->GetImplementation();
+  JS::Rooted<JSObject*> object(aCx, &classObject.toObject());
+  if (impl && !impl->LookupMember(aCx, aName, aNameAsId, aDesc, object)) {
+    return false;
+  }
+  if (aDesc.object() || !mNextBinding) {
+    return true;
+  }
+
+  return mNextBinding->LookupMemberInternal(aCx, aName, aNameAsId, aDesc,
+                                            aXBLScope);
+}
+
+bool
+nsXBLBinding::HasField(nsString& aName)
+{
+  // See if this binding has such a field.
+  return mPrototypeBinding->FindField(aName) ||
+    (mNextBinding && mNextBinding->HasField(aName));
+}
+
+void
+nsXBLBinding::MarkForDeath()
+{
+  mMarkedForDeath = true;
+  ExecuteDetachedHandler();
+}
+
+bool
+nsXBLBinding::ImplementsInterface(REFNSIID aIID) const
+{
+  return mPrototypeBinding->ImplementsInterface(aIID) ||
+    (mNextBinding && mNextBinding->ImplementsInterface(aIID));
+}