diff -r 000000000000 -r 6474c204b198 content/media/MediaTaskQueue.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/media/MediaTaskQueue.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MediaTaskQueue_h_
+#define MediaTaskQueue_h_
+
+#include <queue>
+#include "mozilla/RefPtr.h"
+#include "mozilla/Monitor.h"
+#include "nsThreadUtils.h"
+
+class nsIRunnable;
+
+namespace mozilla {
+
+class SharedThreadPool;
+
+// Abstracts executing runnables in order in a thread pool. The runnables
+// dispatched to the MediaTaskQueue will be executed in the order in which
+// they're received, and are guaranteed to not be executed concurrently.
+// They may be executed on different threads, and a memory barrier is used
+// to make this threadsafe for objects that aren't already threadsafe.
+class MediaTaskQueue MOZ_FINAL {
+  ~MediaTaskQueue();
+
+public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaTaskQueue)
+
+  MediaTaskQueue(TemporaryRef<SharedThreadPool> aPool);
+
+  nsresult Dispatch(TemporaryRef<nsIRunnable> aRunnable);
+
+  // Removes all pending tasks from the task queue, and blocks until
+  // the currently running task (if any) finishes.
+  void Flush();
+
+  // Blocks until all tasks finish executing, then shuts down the task queue
+  // and exits.
+  void Shutdown();
+
+  // Blocks until all task finish executing.
+  void AwaitIdle();
+
+  bool IsEmpty();
+
+  // Returns true if the current thread is currently running a Runnable in
+  // the task queue. This is for debugging/validation purposes only.
+  bool IsCurrentThreadIn();
+
+private:
+
+  // Blocks until all task finish executing. Called internally by methods
+  // that need to wait until the task queue is idle.
+  // mQueueMonitor must be held.
+  void AwaitIdleLocked();
+
+  RefPtr<SharedThreadPool> mPool;
+
+  // Monitor that protects the queue and mIsRunning;
+  Monitor mQueueMonitor;
+
+  // Queue of tasks to run.
+  std::queue<RefPtr<nsIRunnable>> mTasks;
+
+  // The thread currently running the task queue. We store a reference
+  // to this so that IsCurrentThreadIn() can tell if the current thread
+  // is the thread currently running in the task queue.
+  RefPtr<nsIThread> mRunningThread;
+
+  // True if we've dispatched an event to the pool to execute events from
+  // the queue.
+  bool mIsRunning;
+
+  // True if we've started our shutdown process.
+  bool mIsShutdown;
+
+  class Runner : public nsRunnable {
+  public:
+    Runner(MediaTaskQueue* aQueue)
+      : mQueue(aQueue)
+    {
+    }
+    NS_METHOD Run() MOZ_OVERRIDE;
+  private:
+    RefPtr<MediaTaskQueue> mQueue;
+  };
+};
+
+} // namespace mozilla
+
+#endif // MediaTaskQueue_h_