new file mode 100644
--- /dev/null
+++ b/dom/media/FlushableTaskQueue.cpp
@@ -0,0 +1,51 @@
+/* -*- 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 "FlushableTaskQueue.h"
+
+namespace mozilla {
+
+void
+FlushableTaskQueue::Flush()
+{
+  MonitorAutoLock mon(mQueueMonitor);
+  AutoSetFlushing autoFlush(this);
+  FlushLocked();
+  AwaitIdleLocked();
+}
+
+nsresult
+FlushableTaskQueue::FlushAndDispatch(already_AddRefed<nsIRunnable> aRunnable)
+{
+  MonitorAutoLock mon(mQueueMonitor);
+  AutoSetFlushing autoFlush(this);
+  FlushLocked();
+  nsCOMPtr<nsIRunnable> r = dont_AddRef(aRunnable.take());
+  nsresult rv = DispatchLocked(r.forget(), IgnoreFlushing, AssertDispatchSuccess);
+  NS_ENSURE_SUCCESS(rv, rv);
+  AwaitIdleLocked();
+  return NS_OK;
+}
+
+void
+FlushableTaskQueue::FlushLocked()
+{
+  // Make sure there are no tasks for this queue waiting in the caller's tail
+  // dispatcher.
+  MOZ_ASSERT_IF(AbstractThread::GetCurrent(),
+                !AbstractThread::GetCurrent()->TailDispatcher().HasTasksFor(this));
+
+  mQueueMonitor.AssertCurrentThreadOwns();
+  MOZ_ASSERT(mIsFlushing);
+
+  // Clear the tasks. If this strikes you as awful, stop using a
+  // FlushableTaskQueue.
+  while (!mTasks.empty()) {
+    mTasks.pop();
+  }
+}
+
+} // namespace mozilla

new file mode 100644
--- /dev/null
+++ b/dom/media/FlushableTaskQueue.h
@@ -0,0 +1,53 @@
+/* -*- 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 FlushableTaskQueue_h_
+#define FlushableTaskQueue_h_
+
+#include "mozilla/TaskQueue.h"
+
+//
+// WARNING: THIS CLASS IS DEPRECATED AND GOING AWAY. DO NOT USE IT!
+//
+
+namespace mozilla {
+
+class FlushableTaskQueue : public TaskQueue
+{
+public:
+  explicit FlushableTaskQueue(already_AddRefed<SharedThreadPool> aPool) : TaskQueue(Move(aPool)) {}
+  nsresult FlushAndDispatch(already_AddRefed<nsIRunnable> aRunnable);
+  void Flush();
+
+  bool IsDispatchReliable() override { return false; }
+
+private:
+
+  class MOZ_STACK_CLASS AutoSetFlushing
+  {
+  public:
+    explicit AutoSetFlushing(FlushableTaskQueue* aTaskQueue) : mTaskQueue(aTaskQueue)
+    {
+      mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
+      mTaskQueue->mIsFlushing = true;
+    }
+    ~AutoSetFlushing()
+    {
+      mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
+      mTaskQueue->mIsFlushing = false;
+    }
+
+  private:
+    FlushableTaskQueue* mTaskQueue;
+  };
+
+  void FlushLocked();
+
+};
+
+}  // namespace mozilla
+
+#endif // FlushableTaskQueue_h_

--- a/dom/media/TaskQueue.cpp
+++ b/dom/media/TaskQueue.cpp
@@ -169,56 +169,16 @@ TaskQueue::BeginShutdown()
   MonitorAutoLock mon(mQueueMonitor);
   mIsShutdown = true;
   nsRefPtr<ShutdownPromise> p = mShutdownPromise.Ensure(__func__);
   MaybeResolveShutdown();
   mon.NotifyAll();
   return p;
 }
 
-void
-FlushableTaskQueue::Flush()
-{
-  MonitorAutoLock mon(mQueueMonitor);
-  AutoSetFlushing autoFlush(this);
-  FlushLocked();
-  AwaitIdleLocked();
-}
-
-nsresult
-FlushableTaskQueue::FlushAndDispatch(already_AddRefed<nsIRunnable> aRunnable)
-{
-  MonitorAutoLock mon(mQueueMonitor);
-  AutoSetFlushing autoFlush(this);
-  FlushLocked();
-  nsCOMPtr<nsIRunnable> r = dont_AddRef(aRunnable.take());
-  nsresult rv = DispatchLocked(r.forget(), IgnoreFlushing, AssertDispatchSuccess);
-  NS_ENSURE_SUCCESS(rv, rv);
-  AwaitIdleLocked();
-  return NS_OK;
-}
-
-void
-FlushableTaskQueue::FlushLocked()
-{
-  // Make sure there are no tasks for this queue waiting in the caller's tail
-  // dispatcher.
-  MOZ_ASSERT_IF(AbstractThread::GetCurrent(),
-                !AbstractThread::GetCurrent()->TailDispatcher().HasTasksFor(this));
-
-  mQueueMonitor.AssertCurrentThreadOwns();
-  MOZ_ASSERT(mIsFlushing);
-
-  // Clear the tasks. If this strikes you as awful, stop using a
-  // FlushableTaskQueue.
-  while (!mTasks.empty()) {
-    mTasks.pop();
-  }
-}
-
 bool
 TaskQueue::IsEmpty()
 {
   MonitorAutoLock mon(mQueueMonitor);
   return mTasks.empty();
 }
 
 bool

--- a/dom/media/TaskQueue.h
+++ b/dom/media/TaskQueue.h
@@ -170,44 +170,11 @@ protected:
     {
     }
     NS_METHOD Run() override;
   private:
     RefPtr<TaskQueue> mQueue;
   };
 };
 
-class FlushableTaskQueue : public TaskQueue
-{
-public:
-  explicit FlushableTaskQueue(already_AddRefed<SharedThreadPool> aPool) : TaskQueue(Move(aPool)) {}
-  nsresult FlushAndDispatch(already_AddRefed<nsIRunnable> aRunnable);
-  void Flush();
-
-  bool IsDispatchReliable() override { return false; }
-
-private:
-
-  class MOZ_STACK_CLASS AutoSetFlushing
-  {
-  public:
-    explicit AutoSetFlushing(FlushableTaskQueue* aTaskQueue) : mTaskQueue(aTaskQueue)
-    {
-      mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
-      mTaskQueue->mIsFlushing = true;
-    }
-    ~AutoSetFlushing()
-    {
-      mTaskQueue->mQueueMonitor.AssertCurrentThreadOwns();
-      mTaskQueue->mIsFlushing = false;
-    }
-
-  private:
-    FlushableTaskQueue* mTaskQueue;
-  };
-
-  void FlushLocked();
-
-};
-
 } // namespace mozilla
 
 #endif // TaskQueue_h_

--- a/dom/media/moz.build
+++ b/dom/media/moz.build
@@ -105,16 +105,17 @@ EXPORTS += [
     'AudioStream.h',
     'BufferMediaResource.h',
     'CubebUtils.h',
     'DecodedStream.h',
     'DecoderTraits.h',
     'DOMMediaStream.h',
     'EncodedBufferCache.h',
     'FileBlockCache.h',
+    'FlushableTaskQueue.h',
     'Intervals.h',
     'Latency.h',
     'MediaCache.h',
     'MediaData.h',
     'MediaDataDemuxer.h',
     'MediaDecoder.h',
     'MediaDecoderOwner.h',
     'MediaDecoderReader.h',
@@ -202,16 +203,17 @@ UNIFIED_SOURCES += [
     'AudioTrack.cpp',
     'AudioTrackList.cpp',
     'CanvasCaptureMediaStream.cpp',
     'CubebUtils.cpp',
     'DecodedStream.cpp',
     'DOMMediaStream.cpp',
     'EncodedBufferCache.cpp',
     'FileBlockCache.cpp',
+    'FlushableTaskQueue.cpp',
     'GetUserMediaRequest.cpp',
     'GraphDriver.cpp',
     'Latency.cpp',
     'MediaCache.cpp',
     'MediaData.cpp',
     'MediaDecoder.cpp',
     'MediaDecoderReader.cpp',
     'MediaDecoderStateMachine.cpp',

--- a/dom/media/platforms/PlatformDecoderModule.h
+++ b/dom/media/platforms/PlatformDecoderModule.h
@@ -2,16 +2,17 @@
 /* vim:set ts=2 sw=2 sts=2 et cindent: */
 /* 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/. */
 
 #if !defined(PlatformDecoderModule_h_)
 #define PlatformDecoderModule_h_
 
+#include "FlushableTaskQueue.h"
 #include "MediaDecoderReader.h"
 #include "mozilla/MozPromise.h"
 #include "mozilla/layers/LayersTypes.h"
 #include "nsTArray.h"
 #include "mozilla/RefPtr.h"
 #include <queue>
 
 namespace mozilla {

--- a/dom/media/webm/WebMReader.h
+++ b/dom/media/webm/WebMReader.h
@@ -3,16 +3,17 @@
 /* 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/. */
 #if !defined(WebMReader_h_)
 #define WebMReader_h_
 
 #include <stdint.h>
 
+#include "FlushableTaskQueue.h"
 #include "MediaDecoderReader.h"
 #include "PlatformDecoderModule.h"
 #include "nsAutoRef.h"
 #include "nestegg/nestegg.h"
 
 #define VPX_DONT_DEFINE_STDINT_TYPES
 #include "vpx/vpx_codec.h"