Add m-esr52 at 52.6.0

1 files changed, 2666 insertions, 0 deletions

diff --git a/dom/filehandle/ActorsParent.cpp b/dom/filehandle/ActorsParent.cpp
new file mode 100644
index 0000000000..6b81c782f6
--- /dev/null
+++ b/dom/filehandle/ActorsParent.cpp
@@ -0,0 +1,2666 @@
+/* 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 "ActorsParent.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileHandleCommon.h"
+#include "mozilla/dom/PBackgroundFileHandleParent.h"
+#include "mozilla/dom/PBackgroundFileRequestParent.h"
+#include "mozilla/dom/indexedDB/ActorsParent.h"
+#include "mozilla/dom/ipc/BlobParent.h"
+#include "nsAutoPtr.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsIEventTarget.h"
+#include "nsIFileStreams.h"
+#include "nsIInputStream.h"
+#include "nsIOutputStream.h"
+#include "nsIRunnable.h"
+#include "nsISeekableStream.h"
+#include "nsIThread.h"
+#include "nsIThreadPool.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "nsTArray.h"
+#include "nsThreadPool.h"
+#include "nsThreadUtils.h"
+#include "nsXPCOMCIDInternal.h"
+
+#define DISABLE_ASSERTS_FOR_FUZZING 0
+
+#if DISABLE_ASSERTS_FOR_FUZZING
+#define ASSERT_UNLESS_FUZZING(...) do { } while (0)
+#else
+#define ASSERT_UNLESS_FUZZING(...) MOZ_ASSERT(false, __VA_ARGS__)
+#endif
+
+namespace mozilla {
+namespace dom {
+
+using namespace mozilla::ipc;
+
+namespace {
+
+/******************************************************************************
+ * Constants
+ ******************************************************************************/
+
+const uint32_t kThreadLimit = 5;
+const uint32_t kIdleThreadLimit = 1;
+const uint32_t kIdleThreadTimeoutMs = 30000;
+
+const uint32_t kStreamCopyBlockSize = 32768;
+
+} // namespace
+
+class FileHandleThreadPool::FileHandleQueue final
+  : public Runnable
+{
+  friend class FileHandleThreadPool;
+
+  RefPtr<FileHandleThreadPool> mOwningFileHandleThreadPool;
+  RefPtr<FileHandle> mFileHandle;
+  nsTArray<RefPtr<FileHandleOp>> mQueue;
+  RefPtr<FileHandleOp> mCurrentOp;
+  bool mShouldFinish;
+
+public:
+  explicit
+  FileHandleQueue(FileHandleThreadPool* aFileHandleThreadPool,
+                  FileHandle* aFileHandle);
+
+  void
+  Enqueue(FileHandleOp* aFileHandleOp);
+
+  void
+  Finish();
+
+  void
+  ProcessQueue();
+
+private:
+  ~FileHandleQueue() {}
+
+  NS_DECL_NSIRUNNABLE
+};
+
+struct FileHandleThreadPool::DelayedEnqueueInfo
+{
+  RefPtr<FileHandle> mFileHandle;
+  RefPtr<FileHandleOp> mFileHandleOp;
+  bool mFinish;
+};
+
+class FileHandleThreadPool::DirectoryInfo
+{
+  friend class FileHandleThreadPool;
+
+  RefPtr<FileHandleThreadPool> mOwningFileHandleThreadPool;
+  nsTArray<RefPtr<FileHandleQueue>> mFileHandleQueues;
+  nsTArray<DelayedEnqueueInfo> mDelayedEnqueueInfos;
+  nsTHashtable<nsStringHashKey> mFilesReading;
+  nsTHashtable<nsStringHashKey> mFilesWriting;
+
+public:
+  FileHandleQueue*
+  CreateFileHandleQueue(FileHandle* aFileHandle);
+
+  FileHandleQueue*
+  GetFileHandleQueue(FileHandle* aFileHandle);
+
+  void
+  RemoveFileHandleQueue(FileHandle* aFileHandle);
+
+  bool
+  HasRunningFileHandles()
+  {
+    return !mFileHandleQueues.IsEmpty();
+  }
+
+  DelayedEnqueueInfo*
+  CreateDelayedEnqueueInfo(FileHandle* aFileHandle,
+                           FileHandleOp* aFileHandleOp,
+                           bool aFinish);
+
+  void
+  LockFileForReading(const nsAString& aFileName)
+  {
+    mFilesReading.PutEntry(aFileName);
+  }
+
+  void
+  LockFileForWriting(const nsAString& aFileName)
+  {
+    mFilesWriting.PutEntry(aFileName);
+  }
+
+  bool
+  IsFileLockedForReading(const nsAString& aFileName)
+  {
+    return mFilesReading.Contains(aFileName);
+  }
+
+  bool
+  IsFileLockedForWriting(const nsAString& aFileName)
+  {
+    return mFilesWriting.Contains(aFileName);
+  }
+
+private:
+  explicit DirectoryInfo(FileHandleThreadPool* aFileHandleThreadPool)
+    : mOwningFileHandleThreadPool(aFileHandleThreadPool)
+  { }
+};
+
+struct FileHandleThreadPool::StoragesCompleteCallback final
+{
+  friend class nsAutoPtr<StoragesCompleteCallback>;
+
+  nsTArray<nsCString> mDirectoryIds;
+  nsCOMPtr<nsIRunnable> mCallback;
+
+  StoragesCompleteCallback(nsTArray<nsCString>&& aDatabaseIds,
+                           nsIRunnable* aCallback);
+
+private:
+  ~StoragesCompleteCallback();
+};
+
+/******************************************************************************
+ * Actor class declarations
+ ******************************************************************************/
+
+class FileHandle
+  : public PBackgroundFileHandleParent
+{
+  friend class BackgroundMutableFileParentBase;
+
+  class FinishOp;
+
+  RefPtr<BackgroundMutableFileParentBase> mMutableFile;
+  nsCOMPtr<nsISupports> mStream;
+  uint64_t mActiveRequestCount;
+  FileHandleStorage mStorage;
+  Atomic<bool> mInvalidatedOnAnyThread;
+  FileMode mMode;
+  bool mHasBeenActive;
+  bool mActorDestroyed;
+  bool mInvalidated;
+  bool mAborted;
+  bool mFinishOrAbortReceived;
+  bool mFinishedOrAborted;
+  bool mForceAborted;
+
+  DEBUGONLY(nsCOMPtr<nsIEventTarget> mThreadPoolEventTarget;)
+
+public:
+  void
+  AssertIsOnThreadPool() const;
+
+  bool
+  IsActorDestroyed() const
+  {
+    AssertIsOnBackgroundThread();
+
+    return mActorDestroyed;
+  }
+
+  // Must be called on the background thread.
+  bool
+  IsInvalidated() const
+  {
+    MOZ_ASSERT(IsOnBackgroundThread(), "Use IsInvalidatedOnAnyThread()");
+    MOZ_ASSERT_IF(mInvalidated, mAborted);
+
+    return mInvalidated;
+  }
+
+  // May be called on any thread, but is more expensive than IsInvalidated().
+  bool
+  IsInvalidatedOnAnyThread() const
+  {
+    return mInvalidatedOnAnyThread;
+  }
+
+  void
+  SetActive()
+  {
+    AssertIsOnBackgroundThread();
+
+    mHasBeenActive = true;
+  }
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(mozilla::dom::FileHandle)
+
+  nsresult
+  GetOrCreateStream(nsISupports** aStream);
+
+  void
+  Abort(bool aForce);
+
+  FileHandleStorage
+  Storage() const
+  {
+    return mStorage;
+  }
+
+  FileMode
+  Mode() const
+  {
+    return mMode;
+  }
+
+  BackgroundMutableFileParentBase*
+  GetMutableFile() const
+  {
+    AssertIsOnBackgroundThread();
+    MOZ_ASSERT(mMutableFile);
+
+    return mMutableFile;
+  }
+
+  bool
+  IsAborted() const
+  {
+    AssertIsOnBackgroundThread();
+
+    return mAborted;
+  }
+
+  PBackgroundParent*
+  GetBackgroundParent() const
+  {
+    AssertIsOnBackgroundThread();
+    MOZ_ASSERT(!IsActorDestroyed());
+
+    return GetMutableFile()->GetBackgroundParent();
+  }
+
+  void
+  NoteActiveRequest();
+
+  void
+  NoteFinishedRequest();
+
+  void
+  Invalidate();
+
+private:
+  // This constructor is only called by BackgroundMutableFileParentBase.
+  FileHandle(BackgroundMutableFileParentBase* aMutableFile,
+             FileMode aMode);
+
+  // Reference counted.
+  ~FileHandle();
+
+  void
+  MaybeFinishOrAbort()
+  {
+    AssertIsOnBackgroundThread();
+
+    // If we've already finished or aborted then there's nothing else to do.
+    if (mFinishedOrAborted) {
+      return;
+    }
+
+    // If there are active requests then we have to wait for those requests to
+    // complete (see NoteFinishedRequest).
+    if (mActiveRequestCount) {
+      return;
+    }
+
+    // If we haven't yet received a finish or abort message then there could be
+    // additional requests coming so we should wait unless we're being forced to
+    // abort.
+    if (!mFinishOrAbortReceived && !mForceAborted) {
+      return;
+    }
+
+    FinishOrAbort();
+  }
+
+  void
+  SendCompleteNotification(bool aAborted);
+
+  bool
+  VerifyRequestParams(const FileRequestParams& aParams) const;
+
+  bool
+  VerifyRequestData(const FileRequestData& aData) const;
+
+  void
+  FinishOrAbort();
+
+  // IPDL methods are only called by IPDL.
+  virtual void
+  ActorDestroy(ActorDestroyReason aWhy) override;
+
+  virtual bool
+  RecvDeleteMe() override;
+
+  virtual bool
+  RecvFinish() override;
+
+  virtual bool
+  RecvAbort() override;
+
+  virtual PBackgroundFileRequestParent*
+  AllocPBackgroundFileRequestParent(const FileRequestParams& aParams) override;
+
+  virtual bool
+  RecvPBackgroundFileRequestConstructor(PBackgroundFileRequestParent* aActor,
+                                        const FileRequestParams& aParams)
+                                        override;
+
+  virtual bool
+  DeallocPBackgroundFileRequestParent(PBackgroundFileRequestParent* aActor)
+                                      override;
+};
+
+class FileHandleOp
+{
+protected:
+  nsCOMPtr<nsIEventTarget> mOwningThread;
+  RefPtr<FileHandle> mFileHandle;
+
+public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(FileHandleOp)
+
+  void
+  AssertIsOnOwningThread() const
+  {
+    AssertIsOnBackgroundThread();
+    MOZ_ASSERT(mOwningThread);
+    DebugOnly<bool> current;
+    MOZ_ASSERT(NS_SUCCEEDED(mOwningThread->IsOnCurrentThread(&current)));
+    MOZ_ASSERT(current);
+  }
+
+  nsIEventTarget*
+  OwningThread() const
+  {
+    return mOwningThread;
+  }
+
+  void
+  AssertIsOnThreadPool() const
+  {
+    MOZ_ASSERT(mFileHandle);
+    mFileHandle->AssertIsOnThreadPool();
+  }
+
+  void
+  Enqueue();
+
+  virtual void
+  RunOnThreadPool() = 0;
+
+  virtual void
+  RunOnOwningThread() = 0;
+
+protected:
+  FileHandleOp(FileHandle* aFileHandle)
+    : mOwningThread(NS_GetCurrentThread())
+    , mFileHandle(aFileHandle)
+  {
+    AssertIsOnOwningThread();
+    MOZ_ASSERT(aFileHandle);
+  }
+
+  virtual
+  ~FileHandleOp()
+  { }
+};
+
+class FileHandle::FinishOp
+  : public FileHandleOp
+{
+  friend class FileHandle;
+
+  bool mAborted;
+
+private:
+  FinishOp(FileHandle* aFileHandle,
+           bool aAborted)
+    : FileHandleOp(aFileHandle)
+    , mAborted(aAborted)
+  {
+    MOZ_ASSERT(aFileHandle);
+  }
+
+  ~FinishOp()
+  { }
+
+  virtual void
+  RunOnThreadPool() override;
+
+  virtual void
+  RunOnOwningThread() override;
+};
+
+class NormalFileHandleOp
+  : public FileHandleOp
+  , public PBackgroundFileRequestParent
+{
+  nsresult mResultCode;
+  Atomic<bool> mOperationMayProceed;
+  bool mActorDestroyed;
+  const bool mFileHandleIsAborted;
+
+  DEBUGONLY(bool mResponseSent;)
+
+protected:
+  nsCOMPtr<nsISupports> mFileStream;
+
+public:
+  void
+  NoteActorDestroyed()
+  {
+    AssertIsOnOwningThread();
+
+    mActorDestroyed = true;
+    mOperationMayProceed = false;
+  }
+
+  bool
+  IsActorDestroyed() const
+  {
+    AssertIsOnOwningThread();
+
+    return mActorDestroyed;
+  }
+
+  // May be called on any thread, but you should call IsActorDestroyed() if
+  // you know you're on the background thread because it is slightly faster.
+  bool
+  OperationMayProceed() const
+  {
+    return mOperationMayProceed;
+  }
+
+  // May be overridden by subclasses if they need to perform work on the
+  // background thread before being enqueued. Returning false will kill the
+  // child actors and prevent enqueue.
+  virtual bool
+  Init(FileHandle* aFileHandle);
+
+  // This callback will be called on the background thread before releasing the
+  // final reference to this request object. Subclasses may perform any
+  // additional cleanup here but must always call the base class implementation.
+  virtual void
+  Cleanup();
+
+protected:
+  NormalFileHandleOp(FileHandle* aFileHandle)
+    : FileHandleOp(aFileHandle)
+    , mResultCode(NS_OK)
+    , mOperationMayProceed(true)
+    , mActorDestroyed(false)
+    , mFileHandleIsAborted(aFileHandle->IsAborted())
+    DEBUGONLY(, mResponseSent(false))
+  {
+    MOZ_ASSERT(aFileHandle);
+  }
+
+  virtual
+  ~NormalFileHandleOp();
+
+  // Must be overridden in subclasses. Called on the target thread to allow the
+  // subclass to perform necessary file operations. A successful return value
+  // will trigger a SendSuccessResult callback on the background thread while
+  // a failure value will trigger a SendFailureResult callback.
+  virtual nsresult
+  DoFileWork(FileHandle* aFileHandle) = 0;
+
+  // Subclasses use this override to set the IPDL response value.
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) = 0;
+
+private:
+  nsresult
+  SendSuccessResult();
+
+  bool
+  SendFailureResult(nsresult aResultCode);
+
+  virtual void
+  RunOnThreadPool() override;
+
+  virtual void
+  RunOnOwningThread() override;
+
+  // IPDL methods.
+  virtual void
+  ActorDestroy(ActorDestroyReason aWhy) override;
+};
+
+class CopyFileHandleOp
+  : public NormalFileHandleOp
+{
+  class ProgressRunnable;
+
+protected:
+  nsCOMPtr<nsISupports> mBufferStream;
+
+  uint64_t mOffset;
+  uint64_t mSize;
+
+  bool mRead;
+
+protected:
+  CopyFileHandleOp(FileHandle* aFileHandle)
+    : NormalFileHandleOp(aFileHandle)
+    , mOffset(0)
+    , mSize(0)
+    , mRead(true)
+  { }
+
+  virtual nsresult
+  DoFileWork(FileHandle* aFileHandle) override;
+
+  virtual void
+  Cleanup() override;
+};
+
+class CopyFileHandleOp::ProgressRunnable final
+  : public Runnable
+{
+  RefPtr<CopyFileHandleOp> mCopyFileHandleOp;
+  uint64_t mProgress;
+  uint64_t mProgressMax;
+
+public:
+  ProgressRunnable(CopyFileHandleOp* aCopyFileHandleOp,
+                   uint64_t aProgress,
+                   uint64_t aProgressMax)
+    : mCopyFileHandleOp(aCopyFileHandleOp)
+    , mProgress(aProgress)
+    , mProgressMax(aProgressMax)
+  { }
+
+private:
+  ~ProgressRunnable() {}
+
+  NS_DECL_NSIRUNNABLE
+};
+
+class GetMetadataOp
+  : public NormalFileHandleOp
+{
+  friend class FileHandle;
+
+  const FileRequestGetMetadataParams mParams;
+
+protected:
+  FileRequestMetadata mMetadata;
+
+protected:
+  // Only created by FileHandle.
+  GetMetadataOp(FileHandle* aFileHandle,
+                const FileRequestParams& aParams);
+
+  ~GetMetadataOp()
+  { }
+
+  virtual nsresult
+  DoFileWork(FileHandle* aFileHandle) override;
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+class ReadOp final
+  : public CopyFileHandleOp
+{
+  friend class FileHandle;
+
+  class MemoryOutputStream;
+
+  const FileRequestReadParams mParams;
+
+private:
+  // Only created by FileHandle.
+  ReadOp(FileHandle* aFileHandle,
+         const FileRequestParams& aParams);
+
+  ~ReadOp()
+  { }
+
+  virtual bool
+  Init(FileHandle* aFileHandle) override;
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+class ReadOp::MemoryOutputStream final
+  : public nsIOutputStream
+{
+  nsCString mData;
+  uint64_t mOffset;
+
+public:
+  static already_AddRefed<MemoryOutputStream>
+  Create(uint64_t aSize);
+
+  const nsCString&
+  Data() const
+  {
+    return mData;
+  }
+
+private:
+  MemoryOutputStream()
+  : mOffset(0)
+  { }
+
+  virtual ~MemoryOutputStream()
+  { }
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOUTPUTSTREAM
+};
+
+class WriteOp final
+  : public CopyFileHandleOp
+{
+  friend class FileHandle;
+
+  const FileRequestWriteParams mParams;
+
+private:
+  // Only created by FileHandle.
+  WriteOp(FileHandle* aFileHandle,
+          const FileRequestParams& aParams);
+
+  ~WriteOp()
+  { }
+
+  virtual bool
+  Init(FileHandle* aFileHandle) override;
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+class TruncateOp final
+  : public NormalFileHandleOp
+{
+  friend class FileHandle;
+
+  const FileRequestTruncateParams mParams;
+
+private:
+  // Only created by FileHandle.
+  TruncateOp(FileHandle* aFileHandle,
+                        const FileRequestParams& aParams);
+
+  ~TruncateOp()
+  { }
+
+  virtual nsresult
+  DoFileWork(FileHandle* aFileHandle) override;
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+class FlushOp final
+  : public NormalFileHandleOp
+{
+  friend class FileHandle;
+
+  const FileRequestFlushParams mParams;
+
+private:
+  // Only created by FileHandle.
+  FlushOp(FileHandle* aFileHandle,
+          const FileRequestParams& aParams);
+
+  ~FlushOp()
+  { }
+
+  virtual nsresult
+  DoFileWork(FileHandle* aFileHandle) override;
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+class GetFileOp final
+  : public GetMetadataOp
+{
+  friend class FileHandle;
+
+  PBackgroundParent* mBackgroundParent;
+
+private:
+  // Only created by FileHandle.
+  GetFileOp(FileHandle* aFileHandle,
+            const FileRequestParams& aParams);
+
+  ~GetFileOp()
+  { }
+
+  virtual void
+  GetResponse(FileRequestResponse& aResponse) override;
+};
+
+namespace {
+
+/*******************************************************************************
+ * Helper Functions
+ ******************************************************************************/
+
+FileHandleThreadPool*
+GetFileHandleThreadPoolFor(FileHandleStorage aStorage)
+{
+  switch (aStorage) {
+    case FILE_HANDLE_STORAGE_IDB:
+      return mozilla::dom::indexedDB::GetFileHandleThreadPool();
+
+    default:
+      MOZ_CRASH("Bad file handle storage value!");
+  }
+}
+
+} // namespace
+
+/*******************************************************************************
+ * FileHandleThreadPool implementation
+ ******************************************************************************/
+
+FileHandleThreadPool::FileHandleThreadPool()
+  : mOwningThread(NS_GetCurrentThread())
+  , mShutdownRequested(false)
+  , mShutdownComplete(false)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mOwningThread);
+  AssertIsOnOwningThread();
+}
+
+FileHandleThreadPool::~FileHandleThreadPool()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!mDirectoryInfos.Count());
+  MOZ_ASSERT(mCompleteCallbacks.IsEmpty());
+  MOZ_ASSERT(mShutdownRequested);
+  MOZ_ASSERT(mShutdownComplete);
+}
+
+// static
+already_AddRefed<FileHandleThreadPool>
+FileHandleThreadPool::Create()
+{
+  AssertIsOnBackgroundThread();
+
+  RefPtr<FileHandleThreadPool> fileHandleThreadPool =
+    new FileHandleThreadPool();
+  fileHandleThreadPool->AssertIsOnOwningThread();
+
+  if (NS_WARN_IF(NS_FAILED(fileHandleThreadPool->Init()))) {
+    return nullptr;
+  }
+
+  return fileHandleThreadPool.forget();
+}
+
+#ifdef DEBUG
+
+void
+FileHandleThreadPool::AssertIsOnOwningThread() const
+{
+  MOZ_ASSERT(mOwningThread);
+
+  bool current;
+  MOZ_ALWAYS_SUCCEEDS(mOwningThread->IsOnCurrentThread(&current));
+  MOZ_ASSERT(current);
+}
+
+nsIEventTarget*
+FileHandleThreadPool::GetThreadPoolEventTarget() const
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mThreadPool);
+
+  return mThreadPool;
+}
+
+#endif // DEBUG
+
+void
+FileHandleThreadPool::Enqueue(FileHandle* aFileHandle,
+                              FileHandleOp* aFileHandleOp,
+                              bool aFinish)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+  MOZ_ASSERT(!mShutdownRequested);
+
+  BackgroundMutableFileParentBase* mutableFile = aFileHandle->GetMutableFile();
+
+  const nsACString& directoryId = mutableFile->DirectoryId();
+  const nsAString& fileName = mutableFile->FileName();
+  bool modeIsWrite = aFileHandle->Mode() == FileMode::Readwrite;
+
+  DirectoryInfo* directoryInfo;
+  if (!mDirectoryInfos.Get(directoryId, &directoryInfo)) {
+    nsAutoPtr<DirectoryInfo> newDirectoryInfo(new DirectoryInfo(this));
+
+    mDirectoryInfos.Put(directoryId, newDirectoryInfo);
+
+    directoryInfo = newDirectoryInfo.forget();
+  }
+
+  FileHandleQueue* existingFileHandleQueue =
+    directoryInfo->GetFileHandleQueue(aFileHandle);
+
+  if (existingFileHandleQueue) {
+    existingFileHandleQueue->Enqueue(aFileHandleOp);
+    if (aFinish) {
+      existingFileHandleQueue->Finish();
+    }
+    return;
+  }
+
+  bool lockedForReading = directoryInfo->IsFileLockedForReading(fileName);
+  bool lockedForWriting = directoryInfo->IsFileLockedForWriting(fileName);
+
+  if (modeIsWrite) {
+    if (!lockedForWriting) {
+      directoryInfo->LockFileForWriting(fileName);
+    }
+  }
+  else {
+    if (!lockedForReading) {
+      directoryInfo->LockFileForReading(fileName);
+    }
+  }
+
+  if (lockedForWriting || (lockedForReading && modeIsWrite)) {
+    directoryInfo->CreateDelayedEnqueueInfo(aFileHandle,
+                                            aFileHandleOp,
+                                            aFinish);
+  }
+  else {
+    FileHandleQueue* fileHandleQueue =
+      directoryInfo->CreateFileHandleQueue(aFileHandle);
+
+    if (aFileHandleOp) {
+      fileHandleQueue->Enqueue(aFileHandleOp);
+      if (aFinish) {
+        fileHandleQueue->Finish();
+      }
+    }
+  }
+}
+
+void
+FileHandleThreadPool::WaitForDirectoriesToComplete(
+                                             nsTArray<nsCString>&& aDirectoryIds,
+                                             nsIRunnable* aCallback)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!aDirectoryIds.IsEmpty());
+  MOZ_ASSERT(aCallback);
+
+  nsAutoPtr<StoragesCompleteCallback> callback(
+    new StoragesCompleteCallback(Move(aDirectoryIds), aCallback));
+
+  if (!MaybeFireCallback(callback)) {
+    mCompleteCallbacks.AppendElement(callback.forget());
+  }
+}
+
+void
+FileHandleThreadPool::Shutdown()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!mShutdownRequested);
+  MOZ_ASSERT(!mShutdownComplete);
+
+  mShutdownRequested = true;
+
+  if (!mThreadPool) {
+    MOZ_ASSERT(!mDirectoryInfos.Count());
+    MOZ_ASSERT(mCompleteCallbacks.IsEmpty());
+
+    mShutdownComplete = true;
+    return;
+  }
+
+  if (!mDirectoryInfos.Count()) {
+    Cleanup();
+
+    MOZ_ASSERT(mShutdownComplete);
+    return;
+  }
+
+  nsIThread* currentThread = NS_GetCurrentThread();
+  MOZ_ASSERT(currentThread);
+
+  while (!mShutdownComplete) {
+    MOZ_ALWAYS_TRUE(NS_ProcessNextEvent(currentThread));
+  }
+}
+
+nsresult
+FileHandleThreadPool::Init()
+{
+  AssertIsOnOwningThread();
+
+  mThreadPool = new nsThreadPool();
+
+  nsresult rv = mThreadPool->SetName(NS_LITERAL_CSTRING("FileHandles"));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = mThreadPool->SetThreadLimit(kThreadLimit);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = mThreadPool->SetIdleThreadLimit(kIdleThreadLimit);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = mThreadPool->SetIdleThreadTimeout(kIdleThreadTimeoutMs);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+void
+FileHandleThreadPool::Cleanup()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mThreadPool);
+  MOZ_ASSERT(mShutdownRequested);
+  MOZ_ASSERT(!mShutdownComplete);
+  MOZ_ASSERT(!mDirectoryInfos.Count());
+
+  MOZ_ALWAYS_SUCCEEDS(mThreadPool->Shutdown());
+
+  if (!mCompleteCallbacks.IsEmpty()) {
+    // Run all callbacks manually now.
+    for (uint32_t count = mCompleteCallbacks.Length(), index = 0;
+         index < count;
+         index++) {
+      nsAutoPtr<StoragesCompleteCallback> completeCallback(
+        mCompleteCallbacks[index].forget());
+      MOZ_ASSERT(completeCallback);
+      MOZ_ASSERT(completeCallback->mCallback);
+
+      Unused << completeCallback->mCallback->Run();
+    }
+
+    mCompleteCallbacks.Clear();
+
+    // And make sure they get processed.
+    nsIThread* currentThread = NS_GetCurrentThread();
+    MOZ_ASSERT(currentThread);
+
+    MOZ_ALWAYS_SUCCEEDS(NS_ProcessPendingEvents(currentThread));
+  }
+
+  mShutdownComplete = true;
+}
+
+void
+FileHandleThreadPool::FinishFileHandle(FileHandle* aFileHandle)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+
+  BackgroundMutableFileParentBase* mutableFile = aFileHandle->GetMutableFile();
+  const nsACString& directoryId = mutableFile->DirectoryId();
+
+  DirectoryInfo* directoryInfo;
+  if (!mDirectoryInfos.Get(directoryId, &directoryInfo)) {
+    NS_ERROR("We don't know anyting about this directory?!");
+    return;
+  }
+
+  directoryInfo->RemoveFileHandleQueue(aFileHandle);
+
+  if (!directoryInfo->HasRunningFileHandles()) {
+    mDirectoryInfos.Remove(directoryId);
+
+    // See if we need to fire any complete callbacks.
+    uint32_t index = 0;
+    while (index < mCompleteCallbacks.Length()) {
+      if (MaybeFireCallback(mCompleteCallbacks[index])) {
+        mCompleteCallbacks.RemoveElementAt(index);
+      }
+      else {
+        index++;
+      }
+    }
+
+    if (mShutdownRequested && !mDirectoryInfos.Count()) {
+      Cleanup();
+    }
+  }
+}
+
+bool
+FileHandleThreadPool::MaybeFireCallback(StoragesCompleteCallback* aCallback)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aCallback);
+  MOZ_ASSERT(!aCallback->mDirectoryIds.IsEmpty());
+  MOZ_ASSERT(aCallback->mCallback);
+
+  for (uint32_t count = aCallback->mDirectoryIds.Length(), index = 0;
+       index < count;
+       index++) {
+    const nsCString& directoryId = aCallback->mDirectoryIds[index];
+    MOZ_ASSERT(!directoryId.IsEmpty());
+
+    if (mDirectoryInfos.Get(directoryId, nullptr)) {
+      return false;
+    }
+  }
+
+  aCallback->mCallback->Run();
+  return true;
+}
+
+FileHandleThreadPool::
+FileHandleQueue::FileHandleQueue(FileHandleThreadPool* aFileHandleThreadPool,
+                                 FileHandle* aFileHandle)
+  : mOwningFileHandleThreadPool(aFileHandleThreadPool)
+  , mFileHandle(aFileHandle)
+  , mShouldFinish(false)
+{
+  MOZ_ASSERT(aFileHandleThreadPool);
+  aFileHandleThreadPool->AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+}
+
+void
+FileHandleThreadPool::
+FileHandleQueue::Enqueue(FileHandleOp* aFileHandleOp)
+{
+  MOZ_ASSERT(!mShouldFinish, "Enqueue called after Finish!");
+
+  mQueue.AppendElement(aFileHandleOp);
+
+  ProcessQueue();
+}
+
+void
+FileHandleThreadPool::
+FileHandleQueue::Finish()
+{
+  MOZ_ASSERT(!mShouldFinish, "Finish called more than once!");
+
+  mShouldFinish = true;
+}
+
+void
+FileHandleThreadPool::
+FileHandleQueue::ProcessQueue()
+{
+  if (mCurrentOp) {
+    return;
+  }
+
+  if (mQueue.IsEmpty()) {
+    if (mShouldFinish) {
+      mOwningFileHandleThreadPool->FinishFileHandle(mFileHandle);
+
+      // Make sure this is released on this thread.
+      mOwningFileHandleThreadPool = nullptr;
+    }
+
+    return;
+  }
+
+  mCurrentOp = mQueue[0];
+  mQueue.RemoveElementAt(0);
+
+  nsCOMPtr<nsIThreadPool> threadPool = mOwningFileHandleThreadPool->mThreadPool;
+  MOZ_ASSERT(threadPool);
+
+  MOZ_ALWAYS_SUCCEEDS(threadPool->Dispatch(this, NS_DISPATCH_NORMAL));
+}
+
+NS_IMETHODIMP
+FileHandleThreadPool::
+FileHandleQueue::Run()
+{
+  MOZ_ASSERT(mCurrentOp);
+
+  if (IsOnBackgroundThread()) {
+    RefPtr<FileHandleOp> currentOp;
+
+    mCurrentOp.swap(currentOp);
+    ProcessQueue();
+
+    currentOp->RunOnOwningThread();
+  } else {
+    mCurrentOp->RunOnThreadPool();
+
+    nsCOMPtr<nsIEventTarget> backgroundThread = mCurrentOp->OwningThread();
+
+    MOZ_ALWAYS_SUCCEEDS(
+      backgroundThread->Dispatch(this, NS_DISPATCH_NORMAL));
+  }
+
+  return NS_OK;
+}
+
+auto
+FileHandleThreadPool::
+DirectoryInfo::CreateFileHandleQueue(FileHandle* aFileHandle)
+  -> FileHandleQueue*
+{
+  RefPtr<FileHandleQueue>* fileHandleQueue =
+    mFileHandleQueues.AppendElement();
+  *fileHandleQueue = new FileHandleQueue(mOwningFileHandleThreadPool,
+                                         aFileHandle);
+  return fileHandleQueue->get();
+}
+
+auto
+FileHandleThreadPool::
+DirectoryInfo::GetFileHandleQueue(FileHandle* aFileHandle) -> FileHandleQueue*
+{
+  uint32_t count = mFileHandleQueues.Length();
+  for (uint32_t index = 0; index < count; index++) {
+    RefPtr<FileHandleQueue>& fileHandleQueue = mFileHandleQueues[index];
+    if (fileHandleQueue->mFileHandle == aFileHandle) {
+      return fileHandleQueue;
+    }
+  }
+  return nullptr;
+}
+
+void
+FileHandleThreadPool::
+DirectoryInfo::RemoveFileHandleQueue(FileHandle* aFileHandle)
+{
+  for (uint32_t index = 0; index < mDelayedEnqueueInfos.Length(); index++) {
+    if (mDelayedEnqueueInfos[index].mFileHandle == aFileHandle) {
+      MOZ_ASSERT(!mDelayedEnqueueInfos[index].mFileHandleOp, "Should be null!");
+      mDelayedEnqueueInfos.RemoveElementAt(index);
+      return;
+    }
+  }
+
+  uint32_t fileHandleCount = mFileHandleQueues.Length();
+
+  // We can't just remove entries from lock hash tables, we have to rebuild
+  // them instead. Multiple FileHandle objects may lock the same file
+  // (one entry can represent multiple locks).
+
+  mFilesReading.Clear();
+  mFilesWriting.Clear();
+
+  for (uint32_t index = 0, count = fileHandleCount; index < count; index++) {
+    FileHandle* fileHandle = mFileHandleQueues[index]->mFileHandle;
+    if (fileHandle == aFileHandle) {
+      MOZ_ASSERT(count == fileHandleCount, "More than one match?!");
+
+      mFileHandleQueues.RemoveElementAt(index);
+      index--;
+      count--;
+
+      continue;
+    }
+
+    const nsAString& fileName = fileHandle->GetMutableFile()->FileName();
+
+    if (fileHandle->Mode() == FileMode::Readwrite) {
+      if (!IsFileLockedForWriting(fileName)) {
+        LockFileForWriting(fileName);
+      }
+    }
+    else {
+      if (!IsFileLockedForReading(fileName)) {
+        LockFileForReading(fileName);
+      }
+    }
+  }
+
+  MOZ_ASSERT(mFileHandleQueues.Length() == fileHandleCount - 1,
+             "Didn't find the file handle we were looking for!");
+
+  nsTArray<DelayedEnqueueInfo> delayedEnqueueInfos;
+  delayedEnqueueInfos.SwapElements(mDelayedEnqueueInfos);
+
+  for (uint32_t index = 0; index < delayedEnqueueInfos.Length(); index++) {
+    DelayedEnqueueInfo& delayedEnqueueInfo = delayedEnqueueInfos[index];
+    mOwningFileHandleThreadPool->Enqueue(delayedEnqueueInfo.mFileHandle,
+                                         delayedEnqueueInfo.mFileHandleOp,
+                                         delayedEnqueueInfo.mFinish);
+  }
+}
+
+auto
+FileHandleThreadPool::
+DirectoryInfo::CreateDelayedEnqueueInfo(FileHandle* aFileHandle,
+                                        FileHandleOp* aFileHandleOp,
+                                        bool aFinish) -> DelayedEnqueueInfo*
+{
+  DelayedEnqueueInfo* info = mDelayedEnqueueInfos.AppendElement();
+  info->mFileHandle = aFileHandle;
+  info->mFileHandleOp = aFileHandleOp;
+  info->mFinish = aFinish;
+  return info;
+}
+
+FileHandleThreadPool::
+StoragesCompleteCallback::StoragesCompleteCallback(
+                                             nsTArray<nsCString>&& aDirectoryIds,
+                                             nsIRunnable* aCallback)
+  : mDirectoryIds(Move(aDirectoryIds))
+  , mCallback(aCallback)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mDirectoryIds.IsEmpty());
+  MOZ_ASSERT(aCallback);
+
+  MOZ_COUNT_CTOR(FileHandleThreadPool::StoragesCompleteCallback);
+}
+
+FileHandleThreadPool::
+StoragesCompleteCallback::~StoragesCompleteCallback()
+{
+  AssertIsOnBackgroundThread();
+
+  MOZ_COUNT_DTOR(FileHandleThreadPool::StoragesCompleteCallback);
+}
+
+/*******************************************************************************
+ * BackgroundMutableFileParentBase
+ ******************************************************************************/
+
+BackgroundMutableFileParentBase::BackgroundMutableFileParentBase(
+                                                 FileHandleStorage aStorage,
+                                                 const nsACString& aDirectoryId,
+                                                 const nsAString& aFileName,
+                                                 nsIFile* aFile)
+  : mDirectoryId(aDirectoryId)
+  , mFileName(aFileName)
+  , mStorage(aStorage)
+  , mInvalidated(false)
+  , mActorWasAlive(false)
+  , mActorDestroyed(false)
+  , mFile(aFile)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aStorage != FILE_HANDLE_STORAGE_MAX);
+  MOZ_ASSERT(!aDirectoryId.IsEmpty());
+  MOZ_ASSERT(!aFileName.IsEmpty());
+  MOZ_ASSERT(aFile);
+}
+
+BackgroundMutableFileParentBase::~BackgroundMutableFileParentBase()
+{
+  MOZ_ASSERT_IF(mActorWasAlive, mActorDestroyed);
+}
+
+void
+BackgroundMutableFileParentBase::Invalidate()
+{
+  AssertIsOnBackgroundThread();
+
+  class MOZ_STACK_CLASS Helper final
+  {
+  public:
+    static bool
+    InvalidateFileHandles(nsTHashtable<nsPtrHashKey<FileHandle>>& aTable)
+    {
+      AssertIsOnBackgroundThread();
+
+      const uint32_t count = aTable.Count();
+      if (!count) {
+        return true;
+      }
+
+      FallibleTArray<RefPtr<FileHandle>> fileHandles;
+      if (NS_WARN_IF(!fileHandles.SetCapacity(count, fallible))) {
+        return false;
+      }
+
+      for (auto iter = aTable.Iter(); !iter.Done(); iter.Next()) {
+        if (NS_WARN_IF(!fileHandles.AppendElement(iter.Get()->GetKey(),
+                                                  fallible))) {
+          return false;
+        }
+      }
+
+      if (count) {
+        for (uint32_t index = 0; index < count; index++) {
+          RefPtr<FileHandle> fileHandle = fileHandles[index].forget();
+          MOZ_ASSERT(fileHandle);
+
+          fileHandle->Invalidate();
+        }
+      }
+
+      return true;
+    }
+  };
+
+  if (mInvalidated) {
+    return;
+  }
+
+  mInvalidated = true;
+
+  if (!Helper::InvalidateFileHandles(mFileHandles)) {
+    NS_WARNING("Failed to abort all file handles!");
+  }
+}
+
+bool
+BackgroundMutableFileParentBase::RegisterFileHandle(FileHandle* aFileHandle)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileHandle);
+  MOZ_ASSERT(!mFileHandles.GetEntry(aFileHandle));
+  MOZ_ASSERT(!mInvalidated);
+
+  if (NS_WARN_IF(!mFileHandles.PutEntry(aFileHandle, fallible))) {
+    return false;
+  }
+
+  if (mFileHandles.Count() == 1) {
+    NoteActiveState();
+  }
+
+  return true;
+}
+
+void
+BackgroundMutableFileParentBase::UnregisterFileHandle(FileHandle* aFileHandle)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileHandle);
+  MOZ_ASSERT(mFileHandles.GetEntry(aFileHandle));
+
+  mFileHandles.RemoveEntry(aFileHandle);
+
+  if (!mFileHandles.Count()) {
+    NoteInactiveState();
+  }
+}
+
+void
+BackgroundMutableFileParentBase::SetActorAlive()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mActorWasAlive);
+  MOZ_ASSERT(!mActorDestroyed);
+
+  mActorWasAlive = true;
+
+  // This reference will be absorbed by IPDL and released when the actor is
+  // destroyed.
+  AddRef();
+}
+
+already_AddRefed<nsISupports>
+BackgroundMutableFileParentBase::CreateStream(bool aReadOnly)
+{
+  AssertIsOnBackgroundThread();
+
+  nsresult rv;
+
+  if (aReadOnly) {
+    nsCOMPtr<nsIInputStream> stream;
+    rv = NS_NewLocalFileInputStream(getter_AddRefs(stream), mFile, -1, -1,
+                                    nsIFileInputStream::DEFER_OPEN);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return nullptr;
+    }
+    return stream.forget();
+  }
+
+  nsCOMPtr<nsIFileStream> stream;
+  rv = NS_NewLocalFileStream(getter_AddRefs(stream), mFile, -1, -1,
+                             nsIFileStream::DEFER_OPEN);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+  return stream.forget();
+}
+
+void
+BackgroundMutableFileParentBase::ActorDestroy(ActorDestroyReason aWhy)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mActorDestroyed);
+
+  mActorDestroyed = true;
+
+  if (!IsInvalidated()) {
+    Invalidate();
+  }
+}
+
+PBackgroundFileHandleParent*
+BackgroundMutableFileParentBase::AllocPBackgroundFileHandleParent(
+                                                          const FileMode& aMode)
+{
+  AssertIsOnBackgroundThread();
+
+  if (NS_WARN_IF(aMode != FileMode::Readonly &&
+                 aMode != FileMode::Readwrite)) {
+    ASSERT_UNLESS_FUZZING();
+    return nullptr;
+  }
+
+  RefPtr<FileHandle> fileHandle = new FileHandle(this, aMode);
+
+  return fileHandle.forget().take();
+}
+
+bool
+BackgroundMutableFileParentBase::RecvPBackgroundFileHandleConstructor(
+                                            PBackgroundFileHandleParent* aActor,
+                                            const FileMode& aMode)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+  MOZ_ASSERT(aMode == FileMode::Readonly || aMode == FileMode::Readwrite);
+
+  FileHandleThreadPool* fileHandleThreadPool =
+    GetFileHandleThreadPoolFor(mStorage);
+  MOZ_ASSERT(fileHandleThreadPool);
+
+  auto* fileHandle = static_cast<FileHandle*>(aActor);
+
+  // Add a placeholder for this file handle immediately.
+  fileHandleThreadPool->Enqueue(fileHandle, nullptr, false);
+
+  fileHandle->SetActive();
+
+  if (NS_WARN_IF(!RegisterFileHandle(fileHandle))) {
+    fileHandle->Abort(/* aForce */ false);
+    return true;
+  }
+
+  return true;
+}
+
+bool
+BackgroundMutableFileParentBase::DeallocPBackgroundFileHandleParent(
+                                            PBackgroundFileHandleParent* aActor)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  RefPtr<FileHandle> fileHandle =
+    dont_AddRef(static_cast<FileHandle*>(aActor));
+  return true;
+}
+
+bool
+BackgroundMutableFileParentBase::RecvDeleteMe()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mActorDestroyed);
+
+  return PBackgroundMutableFileParent::Send__delete__(this);
+}
+
+bool
+BackgroundMutableFileParentBase::RecvGetFileId(int64_t* aFileId)
+{
+  AssertIsOnBackgroundThread();
+
+  *aFileId = -1;
+  return true;
+}
+
+/*******************************************************************************
+ * FileHandle
+ ******************************************************************************/
+
+FileHandle::FileHandle(BackgroundMutableFileParentBase* aMutableFile,
+                       FileMode aMode)
+  : mMutableFile(aMutableFile)
+  , mActiveRequestCount(0)
+  , mStorage(aMutableFile->Storage())
+  , mInvalidatedOnAnyThread(false)
+  , mMode(aMode)
+  , mHasBeenActive(false)
+  , mActorDestroyed(false)
+  , mInvalidated(false)
+  , mAborted(false)
+  , mFinishOrAbortReceived(false)
+  , mFinishedOrAborted(false)
+  , mForceAborted(false)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aMutableFile);
+
+#ifdef DEBUG
+  FileHandleThreadPool* fileHandleThreadPool =
+    GetFileHandleThreadPoolFor(mStorage);
+  MOZ_ASSERT(fileHandleThreadPool);
+
+  mThreadPoolEventTarget = fileHandleThreadPool->GetThreadPoolEventTarget();
+#endif
+}
+
+FileHandle::~FileHandle()
+{
+  MOZ_ASSERT(!mActiveRequestCount);
+  MOZ_ASSERT(mActorDestroyed);
+  MOZ_ASSERT_IF(mHasBeenActive, mFinishedOrAborted);
+}
+
+void
+FileHandle::AssertIsOnThreadPool() const
+{
+  MOZ_ASSERT(mThreadPoolEventTarget);
+  DebugOnly<bool> current;
+  MOZ_ASSERT(NS_SUCCEEDED(mThreadPoolEventTarget->IsOnCurrentThread(&current)));
+  MOZ_ASSERT(current);
+}
+
+nsresult
+FileHandle::GetOrCreateStream(nsISupports** aStream)
+{
+  AssertIsOnBackgroundThread();
+
+  if (!mStream) {
+    nsCOMPtr<nsISupports> stream =
+      mMutableFile->CreateStream(mMode == FileMode::Readonly);
+    if (NS_WARN_IF(!stream)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    stream.swap(mStream);
+  }
+
+  nsCOMPtr<nsISupports> stream(mStream);
+  stream.forget(aStream);
+
+  return NS_OK;
+}
+
+void
+FileHandle::Abort(bool aForce)
+{
+  AssertIsOnBackgroundThread();
+
+  mAborted = true;
+
+  if (aForce) {
+    mForceAborted = true;
+  }
+
+  MaybeFinishOrAbort();
+}
+
+void
+FileHandle::NoteActiveRequest()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mActiveRequestCount < UINT64_MAX);
+
+  mActiveRequestCount++;
+}
+
+void
+FileHandle::NoteFinishedRequest()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mActiveRequestCount);
+
+  mActiveRequestCount--;
+
+  MaybeFinishOrAbort();
+}
+
+void
+FileHandle::Invalidate()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(mInvalidated == mInvalidatedOnAnyThread);
+
+  if (!mInvalidated) {
+    mInvalidated = true;
+    mInvalidatedOnAnyThread = true;
+
+    Abort(/* aForce */ true);
+  }
+}
+
+void
+FileHandle::SendCompleteNotification(bool aAborted)
+{
+  AssertIsOnBackgroundThread();
+
+  if (!IsActorDestroyed()) {
+    Unused << SendComplete(aAborted);
+  }
+}
+
+bool
+FileHandle::VerifyRequestParams(const FileRequestParams& aParams) const
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aParams.type() != FileRequestParams::T__None);
+
+  switch (aParams.type()) {
+    case FileRequestParams::TFileRequestGetMetadataParams: {
+      const FileRequestGetMetadataParams& params =
+        aParams.get_FileRequestGetMetadataParams();
+
+      if (NS_WARN_IF(!params.size() && !params.lastModified())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestParams::TFileRequestReadParams: {
+      const FileRequestReadParams& params =
+        aParams.get_FileRequestReadParams();
+
+      if (NS_WARN_IF(params.offset() == UINT64_MAX)) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      if (NS_WARN_IF(!params.size())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestParams::TFileRequestWriteParams: {
+      if (NS_WARN_IF(mMode != FileMode::Readwrite)) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      const FileRequestWriteParams& params =
+        aParams.get_FileRequestWriteParams();
+
+
+      if (NS_WARN_IF(!params.dataLength())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      if (NS_WARN_IF(!VerifyRequestData(params.data()))) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestParams::TFileRequestTruncateParams: {
+      if (NS_WARN_IF(mMode != FileMode::Readwrite)) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      const FileRequestTruncateParams& params =
+        aParams.get_FileRequestTruncateParams();
+
+      if (NS_WARN_IF(params.offset() == UINT64_MAX)) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestParams::TFileRequestFlushParams: {
+      if (NS_WARN_IF(mMode != FileMode::Readwrite)) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestParams::TFileRequestGetFileParams: {
+      break;
+    }
+
+    default:
+      MOZ_CRASH("Should never get here!");
+  }
+
+  return true;
+}
+
+bool
+FileHandle::VerifyRequestData(const FileRequestData& aData) const
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aData.type() != FileRequestData::T__None);
+
+  switch (aData.type()) {
+    case FileRequestData::TFileRequestStringData: {
+      const FileRequestStringData& data =
+        aData.get_FileRequestStringData();
+
+      if (NS_WARN_IF(data.string().IsEmpty())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    case FileRequestData::TFileRequestBlobData: {
+      const FileRequestBlobData& data =
+        aData.get_FileRequestBlobData();
+
+      if (NS_WARN_IF(data.blobChild())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      if (NS_WARN_IF(!data.blobParent())) {
+        ASSERT_UNLESS_FUZZING();
+        return false;
+      }
+
+      break;
+    }
+
+    default:
+      MOZ_CRASH("Should never get here!");
+  }
+
+  return true;
+}
+
+void
+FileHandle::FinishOrAbort()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mFinishedOrAborted);
+
+  mFinishedOrAborted = true;
+
+  if (!mHasBeenActive) {
+    return;
+  }
+
+  RefPtr<FinishOp> finishOp = new FinishOp(this, mAborted);
+
+  FileHandleThreadPool* fileHandleThreadPool =
+    GetFileHandleThreadPoolFor(mStorage);
+  MOZ_ASSERT(fileHandleThreadPool);
+
+  fileHandleThreadPool->Enqueue(this, finishOp, true);
+}
+
+void
+FileHandle::ActorDestroy(ActorDestroyReason aWhy)
+{
+  AssertIsOnBackgroundThread();
+
+  MOZ_ASSERT(!mActorDestroyed);
+
+  mActorDestroyed = true;
+
+  if (!mFinishedOrAborted) {
+    mAborted = true;
+
+    mForceAborted = true;
+
+    MaybeFinishOrAbort();
+  }
+}
+
+bool
+FileHandle::RecvDeleteMe()
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!IsActorDestroyed());
+
+  return PBackgroundFileHandleParent::Send__delete__(this);
+}
+
+bool
+FileHandle::RecvFinish()
+{
+  AssertIsOnBackgroundThread();
+
+  if (NS_WARN_IF(mFinishOrAbortReceived)) {
+    ASSERT_UNLESS_FUZZING();
+    return false;
+  }
+
+  mFinishOrAbortReceived = true;
+
+  MaybeFinishOrAbort();
+  return true;
+}
+
+bool
+FileHandle::RecvAbort()
+{
+  AssertIsOnBackgroundThread();
+
+  if (NS_WARN_IF(mFinishOrAbortReceived)) {
+    ASSERT_UNLESS_FUZZING();
+    return false;
+  }
+
+  mFinishOrAbortReceived = true;
+
+  Abort(/* aForce */ false);
+  return true;
+}
+
+PBackgroundFileRequestParent*
+FileHandle::AllocPBackgroundFileRequestParent(const FileRequestParams& aParams)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aParams.type() != FileRequestParams::T__None);
+
+#ifdef DEBUG
+  // Always verify parameters in DEBUG builds!
+  bool trustParams = false;
+#else
+  PBackgroundParent* backgroundActor = GetBackgroundParent();
+  MOZ_ASSERT(backgroundActor);
+
+  bool trustParams = !BackgroundParent::IsOtherProcessActor(backgroundActor);
+#endif
+
+  if (NS_WARN_IF(!trustParams && !VerifyRequestParams(aParams))) {
+    ASSERT_UNLESS_FUZZING();
+    return nullptr;
+  }
+
+  if (NS_WARN_IF(mFinishOrAbortReceived)) {
+    ASSERT_UNLESS_FUZZING();
+    return nullptr;
+  }
+
+  RefPtr<NormalFileHandleOp> actor;
+
+  switch (aParams.type()) {
+    case FileRequestParams::TFileRequestGetMetadataParams:
+      actor = new GetMetadataOp(this, aParams);
+      break;
+
+    case FileRequestParams::TFileRequestReadParams:
+      actor = new ReadOp(this, aParams);
+      break;
+
+    case FileRequestParams::TFileRequestWriteParams:
+      actor = new WriteOp(this, aParams);
+      break;
+
+    case FileRequestParams::TFileRequestTruncateParams:
+      actor = new TruncateOp(this, aParams);
+      break;
+
+    case FileRequestParams::TFileRequestFlushParams:
+      actor = new FlushOp(this, aParams);
+      break;
+
+    case FileRequestParams::TFileRequestGetFileParams:
+      actor = new GetFileOp(this, aParams);
+      break;
+
+    default:
+      MOZ_CRASH("Should never get here!");
+  }
+
+  MOZ_ASSERT(actor);
+
+  // Transfer ownership to IPDL.
+  return actor.forget().take();
+}
+
+bool
+FileHandle::RecvPBackgroundFileRequestConstructor(
+                                           PBackgroundFileRequestParent* aActor,
+                                           const FileRequestParams& aParams)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+  MOZ_ASSERT(aParams.type() != FileRequestParams::T__None);
+
+  auto* op = static_cast<NormalFileHandleOp*>(aActor);
+
+  if (NS_WARN_IF(!op->Init(this))) {
+    op->Cleanup();
+    return false;
+  }
+
+  op->Enqueue();
+  return true;
+}
+
+bool
+FileHandle::DeallocPBackgroundFileRequestParent(
+                                           PBackgroundFileRequestParent* aActor)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aActor);
+
+  // Transfer ownership back from IPDL.
+  RefPtr<NormalFileHandleOp> actor =
+    dont_AddRef(static_cast<NormalFileHandleOp*>(aActor));
+  return true;
+}
+
+/*******************************************************************************
+ * Local class implementations
+ ******************************************************************************/
+
+void
+FileHandleOp::Enqueue()
+{
+  AssertIsOnOwningThread();
+
+  FileHandleThreadPool* fileHandleThreadPool =
+    GetFileHandleThreadPoolFor(mFileHandle->Storage());
+  MOZ_ASSERT(fileHandleThreadPool);
+
+  fileHandleThreadPool->Enqueue(mFileHandle, this, false);
+
+  mFileHandle->NoteActiveRequest();
+}
+
+void
+FileHandle::
+FinishOp::RunOnThreadPool()
+{
+  AssertIsOnThreadPool();
+  MOZ_ASSERT(mFileHandle);
+
+  nsCOMPtr<nsISupports>& stream = mFileHandle->mStream;
+
+  if (!stream) {
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream = do_QueryInterface(stream);
+  MOZ_ASSERT(inputStream);
+
+  MOZ_ALWAYS_SUCCEEDS(inputStream->Close());
+
+  stream = nullptr;
+}
+
+void
+FileHandle::
+FinishOp::RunOnOwningThread()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mFileHandle);
+
+  mFileHandle->SendCompleteNotification(mAborted);
+
+  mFileHandle->GetMutableFile()->UnregisterFileHandle(mFileHandle);
+
+  mFileHandle = nullptr;
+}
+
+NormalFileHandleOp::~NormalFileHandleOp()
+{
+  MOZ_ASSERT(!mFileHandle,
+             "NormalFileHandleOp::Cleanup() was not called by a subclass!");
+}
+
+bool
+NormalFileHandleOp::Init(FileHandle* aFileHandle)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+
+  nsresult rv = aFileHandle->GetOrCreateStream(getter_AddRefs(mFileStream));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return false;
+  }
+
+  return true;
+}
+
+void
+NormalFileHandleOp::Cleanup()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mFileHandle);
+  MOZ_ASSERT_IF(!IsActorDestroyed(), mResponseSent);
+
+  mFileHandle = nullptr;
+}
+
+nsresult
+NormalFileHandleOp::SendSuccessResult()
+{
+  AssertIsOnOwningThread();
+
+  if (!IsActorDestroyed()) {
+    FileRequestResponse response;
+    GetResponse(response);
+
+    MOZ_ASSERT(response.type() != FileRequestResponse::T__None);
+
+    if (response.type() == FileRequestResponse::Tnsresult) {
+      MOZ_ASSERT(NS_FAILED(response.get_nsresult()));
+
+      return response.get_nsresult();
+    }
+
+    if (NS_WARN_IF(!PBackgroundFileRequestParent::Send__delete__(this,
+                                                                 response))) {
+      return NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+    }
+  }
+
+  DEBUGONLY(mResponseSent = true;)
+
+  return NS_OK;
+}
+
+bool
+NormalFileHandleOp::SendFailureResult(nsresult aResultCode)
+{
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(NS_FAILED(aResultCode));
+
+  bool result = false;
+
+  if (!IsActorDestroyed()) {
+    result =
+      PBackgroundFileRequestParent::Send__delete__(this, aResultCode);
+  }
+
+  DEBUGONLY(mResponseSent = true;)
+
+  return result;
+}
+
+void
+NormalFileHandleOp::RunOnThreadPool()
+{
+  AssertIsOnThreadPool();
+  MOZ_ASSERT(mFileHandle);
+  MOZ_ASSERT(NS_SUCCEEDED(mResultCode));
+
+  // There are several cases where we don't actually have to to any work here.
+
+  if (mFileHandleIsAborted) {
+    // This transaction is already set to be aborted.
+    mResultCode = NS_ERROR_DOM_FILEHANDLE_ABORT_ERR;
+  } else if (mFileHandle->IsInvalidatedOnAnyThread()) {
+    // This file handle is being invalidated.
+    mResultCode = NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+  } else if (!OperationMayProceed()) {
+    // The operation was canceled in some way, likely because the child process
+    // has crashed.
+    mResultCode = NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+  } else {
+    nsresult rv = DoFileWork(mFileHandle);
+    if (NS_FAILED(rv)) {
+      mResultCode = rv;
+    }
+  }
+}
+
+void
+NormalFileHandleOp::RunOnOwningThread()
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mFileHandle);
+
+  if (NS_WARN_IF(IsActorDestroyed())) {
+    // Don't send any notifications if the actor was destroyed already.
+    if (NS_SUCCEEDED(mResultCode)) {
+      mResultCode = NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+    }
+  } else {
+    if (mFileHandle->IsInvalidated()) {
+      mResultCode = NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+    } else if (mFileHandle->IsAborted()) {
+      // Aborted file handles always see their requests fail with ABORT_ERR,
+      // even if the request succeeded or failed with another error.
+      mResultCode = NS_ERROR_DOM_FILEHANDLE_ABORT_ERR;
+    } else if (NS_SUCCEEDED(mResultCode)) {
+      // This may release the IPDL reference.
+      mResultCode = SendSuccessResult();
+    }
+
+    if (NS_FAILED(mResultCode)) {
+      // This should definitely release the IPDL reference.
+      if (!SendFailureResult(mResultCode)) {
+        // Abort the file handle.
+        mFileHandle->Abort(/* aForce */ false);
+      }
+    }
+  }
+
+  mFileHandle->NoteFinishedRequest();
+
+  Cleanup();
+}
+
+void
+NormalFileHandleOp::ActorDestroy(ActorDestroyReason aWhy)
+{
+  AssertIsOnOwningThread();
+
+  NoteActorDestroyed();
+}
+
+nsresult
+CopyFileHandleOp::DoFileWork(FileHandle* aFileHandle)
+{
+  AssertIsOnThreadPool();
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  nsCOMPtr<nsIOutputStream> outputStream;
+
+  if (mRead) {
+    inputStream = do_QueryInterface(mFileStream);
+    outputStream = do_QueryInterface(mBufferStream);
+  } else {
+    inputStream = do_QueryInterface(mBufferStream);
+    outputStream = do_QueryInterface(mFileStream);
+  }
+
+  MOZ_ASSERT(inputStream);
+  MOZ_ASSERT(outputStream);
+
+  nsCOMPtr<nsISeekableStream> seekableStream =
+    do_QueryInterface(mFileStream);
+
+  nsresult rv;
+
+  if (seekableStream) {
+    if (mOffset == UINT64_MAX) {
+      rv = seekableStream->Seek(nsISeekableStream::NS_SEEK_END, 0);
+    }
+    else {
+      rv = seekableStream->Seek(nsISeekableStream::NS_SEEK_SET, mOffset);
+    }
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  mOffset = 0;
+
+  do {
+    char copyBuffer[kStreamCopyBlockSize];
+
+    uint64_t max = mSize - mOffset;
+    if (max == 0) {
+      break;
+    }
+
+    uint32_t count = sizeof(copyBuffer);
+    if (count > max) {
+      count = max;
+    }
+
+    uint32_t numRead;
+    rv = inputStream->Read(copyBuffer, count, &numRead);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    if (!numRead) {
+      break;
+    }
+
+    uint32_t numWrite;
+    rv = outputStream->Write(copyBuffer, numRead, &numWrite);
+    if (rv == NS_ERROR_FILE_NO_DEVICE_SPACE) {
+      rv = NS_ERROR_DOM_FILEHANDLE_QUOTA_ERR;
+    }
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    if (NS_WARN_IF(numWrite != numRead)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    mOffset += numWrite;
+
+    nsCOMPtr<nsIRunnable> runnable =
+      new ProgressRunnable(this, mOffset, mSize);
+
+    mOwningThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  } while (true);
+
+  MOZ_ASSERT(mOffset == mSize);
+
+  if (mRead) {
+    MOZ_ALWAYS_SUCCEEDS(outputStream->Close());
+  } else {
+    MOZ_ALWAYS_SUCCEEDS(inputStream->Close());
+  }
+
+  return NS_OK;
+}
+
+void
+CopyFileHandleOp::Cleanup()
+{
+  AssertIsOnOwningThread();
+
+  mBufferStream = nullptr;
+
+  NormalFileHandleOp::Cleanup();
+}
+
+NS_IMETHODIMP
+CopyFileHandleOp::
+ProgressRunnable::Run()
+{
+  AssertIsOnBackgroundThread();
+
+  Unused << mCopyFileHandleOp->SendProgress(mProgress, mProgressMax);
+
+  mCopyFileHandleOp = nullptr;
+
+  return NS_OK;
+}
+
+GetMetadataOp::GetMetadataOp(FileHandle* aFileHandle,
+                             const FileRequestParams& aParams)
+  : NormalFileHandleOp(aFileHandle)
+  , mParams(aParams.get_FileRequestGetMetadataParams())
+{
+  MOZ_ASSERT(aParams.type() ==
+             FileRequestParams::TFileRequestGetMetadataParams);
+}
+
+nsresult
+GetMetadataOp::DoFileWork(FileHandle* aFileHandle)
+{
+  AssertIsOnThreadPool();
+
+  nsresult rv;
+
+  if (mFileHandle->Mode() == FileMode::Readwrite) {
+    // Force a flush (so all pending writes are flushed to the disk and file
+    // metadata is updated too).
+
+    nsCOMPtr<nsIOutputStream> ostream = do_QueryInterface(mFileStream);
+    MOZ_ASSERT(ostream);
+
+    rv = ostream->Flush();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  nsCOMPtr<nsIFileMetadata> metadata = do_QueryInterface(mFileStream);
+  MOZ_ASSERT(metadata);
+
+  if (mParams.size()) {
+    int64_t size;
+    rv = metadata->GetSize(&size);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    if (NS_WARN_IF(size < 0)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    mMetadata.size() = uint64_t(size);
+  } else {
+    mMetadata.size() = void_t();
+  }
+
+  if (mParams.lastModified()) {
+    int64_t lastModified;
+    rv = metadata->GetLastModified(&lastModified);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    mMetadata.lastModified() = lastModified;
+  } else {
+    mMetadata.lastModified() = void_t();
+  }
+
+  return NS_OK;
+}
+
+void
+GetMetadataOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+
+  aResponse = FileRequestGetMetadataResponse(mMetadata);
+}
+
+ReadOp::ReadOp(FileHandle* aFileHandle,
+               const FileRequestParams& aParams)
+  : CopyFileHandleOp(aFileHandle)
+  , mParams(aParams.get_FileRequestReadParams())
+{
+  MOZ_ASSERT(aParams.type() == FileRequestParams::TFileRequestReadParams);
+}
+
+bool
+ReadOp::Init(FileHandle* aFileHandle)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+
+  if (NS_WARN_IF(!NormalFileHandleOp::Init(aFileHandle))) {
+    return false;
+  }
+
+  mBufferStream = MemoryOutputStream::Create(mParams.size());
+  if (NS_WARN_IF(!mBufferStream)) {
+    return false;
+  }
+
+  mOffset = mParams.offset();
+  mSize = mParams.size();
+  mRead = true;
+
+  return true;
+}
+
+void
+ReadOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+
+  auto* stream = static_cast<MemoryOutputStream*>(mBufferStream.get());
+
+  aResponse = FileRequestReadResponse(stream->Data());
+}
+
+// static
+already_AddRefed<ReadOp::MemoryOutputStream>
+ReadOp::
+MemoryOutputStream::Create(uint64_t aSize)
+{
+  MOZ_ASSERT(aSize, "Passed zero size!");
+
+  if (NS_WARN_IF(aSize > UINT32_MAX)) {
+    return nullptr;
+  }
+
+  RefPtr<MemoryOutputStream> stream = new MemoryOutputStream();
+
+  char* dummy;
+  uint32_t length = stream->mData.GetMutableData(&dummy, aSize, fallible);
+  if (NS_WARN_IF(length != aSize)) {
+    return nullptr;
+  }
+
+  return stream.forget();
+}
+
+NS_IMPL_ISUPPORTS(ReadOp::MemoryOutputStream, nsIOutputStream)
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::Close()
+{
+  mData.Truncate(mOffset);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::Write(const char* aBuf, uint32_t aCount, uint32_t* _retval)
+{
+  return WriteSegments(NS_CopySegmentToBuffer, (char*)aBuf, aCount, _retval);
+}
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::Flush()
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::WriteFrom(nsIInputStream* aFromStream, uint32_t aCount,
+                              uint32_t* _retval)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::WriteSegments(nsReadSegmentFun aReader, void* aClosure,
+                                  uint32_t aCount, uint32_t* _retval)
+{
+  NS_ASSERTION(mData.Length() >= mOffset, "Bad stream state!");
+
+  uint32_t maxCount = mData.Length() - mOffset;
+  if (maxCount == 0) {
+    *_retval = 0;
+    return NS_OK;
+  }
+
+  if (aCount > maxCount) {
+    aCount = maxCount;
+  }
+
+  nsresult rv = aReader(this, aClosure, mData.BeginWriting() + mOffset, 0,
+                        aCount, _retval);
+  if (NS_SUCCEEDED(rv)) {
+    NS_ASSERTION(*_retval <= aCount,
+                 "Reader should not read more than we asked it to read!");
+    mOffset += *_retval;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ReadOp::
+MemoryOutputStream::IsNonBlocking(bool* _retval)
+{
+  *_retval = false;
+  return NS_OK;
+}
+
+WriteOp::WriteOp(FileHandle* aFileHandle,
+                 const FileRequestParams& aParams)
+  : CopyFileHandleOp(aFileHandle)
+  , mParams(aParams.get_FileRequestWriteParams())
+{
+  MOZ_ASSERT(aParams.type() == FileRequestParams::TFileRequestWriteParams);
+}
+
+bool
+WriteOp::Init(FileHandle* aFileHandle)
+{
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFileHandle);
+
+  if (NS_WARN_IF(!NormalFileHandleOp::Init(aFileHandle))) {
+    return false;
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  const FileRequestData& data = mParams.data();
+  switch (data.type()) {
+    case FileRequestData::TFileRequestStringData: {
+      const FileRequestStringData& stringData =
+        data.get_FileRequestStringData();
+
+      const nsCString& string = stringData.string();
+
+      nsresult rv =
+        NS_NewCStringInputStream(getter_AddRefs(inputStream), string);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return false;
+      }
+
+      break;
+    }
+    case FileRequestData::TFileRequestBlobData: {
+      const FileRequestBlobData& blobData =
+        data.get_FileRequestBlobData();
+
+      auto blobActor = static_cast<BlobParent*>(blobData.blobParent());
+
+      RefPtr<BlobImpl> blobImpl = blobActor->GetBlobImpl();
+
+      ErrorResult rv;
+      blobImpl->GetInternalStream(getter_AddRefs(inputStream), rv);
+      if (NS_WARN_IF(rv.Failed())) {
+        rv.SuppressException();
+        return false;
+      }
+
+      break;
+    }
+
+    default:
+      MOZ_CRASH("Should never get here!");
+  }
+
+  mBufferStream = inputStream;
+  mOffset = mParams.offset();
+  mSize = mParams.dataLength();
+  mRead = false;
+
+  return true;
+}
+
+void
+WriteOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+  aResponse = FileRequestWriteResponse();
+}
+
+TruncateOp::TruncateOp(FileHandle* aFileHandle,
+                       const FileRequestParams& aParams)
+  : NormalFileHandleOp(aFileHandle)
+  , mParams(aParams.get_FileRequestTruncateParams())
+{
+  MOZ_ASSERT(aParams.type() == FileRequestParams::TFileRequestTruncateParams);
+}
+
+nsresult
+TruncateOp::DoFileWork(FileHandle* aFileHandle)
+{
+  AssertIsOnThreadPool();
+
+  nsCOMPtr<nsISeekableStream> sstream = do_QueryInterface(mFileStream);
+  MOZ_ASSERT(sstream);
+
+  nsresult rv = sstream->Seek(nsISeekableStream::NS_SEEK_SET, mParams.offset());
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = sstream->SetEOF();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+void
+TruncateOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+  aResponse = FileRequestTruncateResponse();
+}
+
+FlushOp::FlushOp(FileHandle* aFileHandle,
+                 const FileRequestParams& aParams)
+  : NormalFileHandleOp(aFileHandle)
+  , mParams(aParams.get_FileRequestFlushParams())
+{
+  MOZ_ASSERT(aParams.type() == FileRequestParams::TFileRequestFlushParams);
+}
+
+nsresult
+FlushOp::DoFileWork(FileHandle* aFileHandle)
+{
+  AssertIsOnThreadPool();
+
+  nsCOMPtr<nsIOutputStream> ostream = do_QueryInterface(mFileStream);
+  MOZ_ASSERT(ostream);
+
+  nsresult rv = ostream->Flush();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+void
+FlushOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+  aResponse = FileRequestFlushResponse();
+}
+
+GetFileOp::GetFileOp(FileHandle* aFileHandle,
+                     const FileRequestParams& aParams)
+  : GetMetadataOp(aFileHandle,
+                  FileRequestGetMetadataParams(true, true))
+  , mBackgroundParent(aFileHandle->GetBackgroundParent())
+{
+  MOZ_ASSERT(aParams.type() == FileRequestParams::TFileRequestGetFileParams);
+  MOZ_ASSERT(mBackgroundParent);
+}
+
+void
+GetFileOp::GetResponse(FileRequestResponse& aResponse)
+{
+  AssertIsOnOwningThread();
+
+  RefPtr<BlobImpl> blobImpl = mFileHandle->GetMutableFile()->CreateBlobImpl();
+  MOZ_ASSERT(blobImpl);
+
+  PBlobParent* actor =
+    BackgroundParent::GetOrCreateActorForBlobImpl(mBackgroundParent, blobImpl);
+  if (NS_WARN_IF(!actor)) {
+    // This can only fail if the child has crashed.
+    aResponse = NS_ERROR_DOM_FILEHANDLE_UNKNOWN_ERR;
+    return;
+  }
+
+  FileRequestGetFileResponse response;
+  response.fileParent() = actor;
+  response.metadata() = mMetadata;
+
+  aResponse = response;
+}
+
+} // namespace dom
+} // namespace mozilla