diff --git a/dom/media/MediaDecoderReader.cpp b/dom/media/MediaDecoderReader.cpp
index 44ca2d92278..26698623d5b 100644
--- a/dom/media/MediaDecoderReader.cpp
+++ b/dom/media/MediaDecoderReader.cpp
@@ -283,18 +283,28 @@ MediaDecoderReader::BreakCycles()
   mTaskQueue = nullptr;
 }
 
-void
+nsRefPtr<ShutdownPromise>
 MediaDecoderReader::Shutdown()
 {
   MOZ_ASSERT(OnDecodeThread());
   mShutdown = true;
   ReleaseMediaResources();
+  nsRefPtr<ShutdownPromise> p;
+
+  // Spin down the task queue if necessary. We wait until BreakCycles to null
+  // out mTaskQueue, since otherwise any remaining tasks could crash when they
+  // invoke GetTaskQueue()->IsCurrentThreadIn().
   if (mTaskQueue && !mTaskQueueIsBorrowed) {
-    // We may be running in the task queue ourselves, so we don't block this
-    // thread on task queue draining, since that would deadlock.
-    mTaskQueue->BeginShutdown();
+    // If we own our task queue, shutdown ends when the task queue is done.
+    p = mTaskQueue->BeginShutdown();
+  } else {
+    // If we don't own our task queue, we resolve immediately (though
+    // asynchronously).
+    p = new ShutdownPromise(__func__);
+    p->Resolve(true, __func__);
   }
-  mTaskQueue = nullptr;
+
+  return p;
 }
 
 AudioDecodeRendezvous::AudioDecodeRendezvous()
diff --git a/dom/media/MediaDecoderReader.h b/dom/media/MediaDecoderReader.h
index 508ee8fa8bd..eaee9c0c33a 100644
--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -65,7 +65,7 @@ public:
   // This is different from ReleaseMediaResources() as it is irreversable,
   // whereas ReleaseMediaResources() is.  Must be called on the decode
   // thread.
-  virtual void Shutdown();
+  virtual nsRefPtr<ShutdownPromise> Shutdown();
 
   virtual void SetCallback(RequestSampleCallback* aDecodedSampleCallback);
   MediaTaskQueue* EnsureTaskQueue();
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 798f0860ba3..9f899eb2215 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2470,6 +2470,53 @@ private:
   nsRefPtr<MediaDecoderStateMachine> mStateMachine;
 };
 
+void
+MediaDecoderStateMachine::ShutdownReader()
+{
+  MOZ_ASSERT(OnDecodeThread());
+  mReader->Shutdown()->Then(GetStateMachineThread(), __func__, this,
+                            &MediaDecoderStateMachine::FinishShutdown,
+                            &MediaDecoderStateMachine::FinishShutdown);
+}
+
+void
+MediaDecoderStateMachine::FinishShutdown(bool aSuccess)
+{
+  MOZ_ASSERT(OnStateMachineThread());
+  MOZ_ASSERT(aSuccess);
+  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
+
+  // The reader's listeners hold references to the state machine,
+  // creating a cycle which keeps the state machine and its shared
+  // thread pools alive. So break it here.
+  AudioQueue().ClearListeners();
+  VideoQueue().ClearListeners();
+
+  // Now that those threads are stopped, there's no possibility of
+  // mPendingWakeDecoder being needed again. Revoke it.
+  mPendingWakeDecoder = nullptr;
+
+  MOZ_ASSERT(mState == DECODER_STATE_SHUTDOWN,
+             "How did we escape from the shutdown state?");
+  // We must daisy-chain these events to destroy the decoder. We must
+  // destroy the decoder on the main thread, but we can't destroy the
+  // decoder while this thread holds the decoder monitor. We can't
+  // dispatch an event to the main thread to destroy the decoder from
+  // here, as the event may run before the dispatch returns, and we
+  // hold the decoder monitor here. We also want to guarantee that the
+  // state machine is destroyed on the main thread, and so the
+  // event runner running this function (which holds a reference to the
+  // state machine) needs to finish and be released in order to allow
+  // that. So we dispatch an event to run after this event runner has
+  // finished and released its monitor/references. That event then will
+  // dispatch an event to the main thread to release the decoder and
+  // state machine.
+  GetStateMachineThread()->Dispatch(
+    new nsDispatchDisposeEvent(mDecoder, this), NS_DISPATCH_NORMAL);
+
+  DECODER_LOG("Dispose Event Dispatched");
+}
+
 nsresult MediaDecoderStateMachine::RunStateMachine()
 {
   AssertCurrentThreadInMonitor();
@@ -2486,47 +2533,14 @@ nsresult MediaDecoderStateMachine::RunStateMachine()
       StopAudioThread();
       FlushDecoding();
 
-      // Put a task in the decode queue to shutdown the reader and wait for
+      // Put a task in the decode queue to shutdown the reader.
       // the queue to spin down.
-      {
-        RefPtr<nsIRunnable> task;
-        task = NS_NewRunnableMethod(mReader, &MediaDecoderReader::Shutdown);
-        nsRefPtr<MediaTaskQueue> queue = DecodeTaskQueue();
-        DebugOnly<nsresult> rv = queue->Dispatch(task);
-        MOZ_ASSERT(NS_SUCCEEDED(rv));
-        ReentrantMonitorAutoExit exitMon(mDecoder->GetReentrantMonitor());
-        queue->AwaitShutdownAndIdle();
-      }
+      RefPtr<nsIRunnable> task;
+      task = NS_NewRunnableMethod(this, &MediaDecoderStateMachine::ShutdownReader);
+      DebugOnly<nsresult> rv = DecodeTaskQueue()->Dispatch(task);
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
 
-      // The reader's listeners hold references to the state machine,
-      // creating a cycle which keeps the state machine and its shared
-      // thread pools alive. So break it here.
-      AudioQueue().ClearListeners();
-      VideoQueue().ClearListeners();
-
-      // Now that those threads are stopped, there's no possibility of
-      // mPendingWakeDecoder being needed again. Revoke it.
-      mPendingWakeDecoder = nullptr;
-
-      MOZ_ASSERT(mState == DECODER_STATE_SHUTDOWN,
-                 "How did we escape from the shutdown state?");
-      // We must daisy-chain these events to destroy the decoder. We must
-      // destroy the decoder on the main thread, but we can't destroy the
-      // decoder while this thread holds the decoder monitor. We can't
-      // dispatch an event to the main thread to destroy the decoder from
-      // here, as the event may run before the dispatch returns, and we
-      // hold the decoder monitor here. We also want to guarantee that the
-      // state machine is destroyed on the main thread, and so the
-      // event runner running this function (which holds a reference to the
-      // state machine) needs to finish and be released in order to allow
-      // that. So we dispatch an event to run after this event runner has
-      // finished and released its monitor/references. That event then will
-      // dispatch an event to the main thread to release the decoder and
-      // state machine.
-      GetStateMachineThread()->Dispatch(
-        new nsDispatchDisposeEvent(mDecoder, this), NS_DISPATCH_NORMAL);
-
-      DECODER_LOG("SHUTDOWN OK");
+      DECODER_LOG("Shutdown started");
       return NS_OK;
     }
 
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index dfcbf5734a4..d99195c703a 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -162,6 +162,8 @@ public:
   // Set/Unset dormant state.
   void SetDormant(bool aDormant);
   void Shutdown();
+  void ShutdownReader();
+  void FinishShutdown(bool aSuccess);
 
   // Called from the main thread to get the duration. The decoder monitor
   // must be obtained before calling this. It is in units of microseconds.
diff --git a/dom/media/MediaTaskQueue.cpp b/dom/media/MediaTaskQueue.cpp
index 7afd582da4a..78235612138 100644
--- a/dom/media/MediaTaskQueue.cpp
+++ b/dom/media/MediaTaskQueue.cpp
@@ -134,12 +134,17 @@ MediaTaskQueue::AwaitShutdownAndIdle()
   AwaitIdleLocked();
 }
 
-void
+nsRefPtr<ShutdownPromise>
 MediaTaskQueue::BeginShutdown()
 {
   MonitorAutoLock mon(mQueueMonitor);
   mIsShutdown = true;
+  nsRefPtr<ShutdownPromise> p = mShutdownPromise.Ensure(__func__);
+  if (!mIsRunning) {
+    mShutdownPromise.Resolve(true, __func__);
+  }
   mon.NotifyAll();
+  return p;
 }
 
 nsresult
@@ -208,6 +213,7 @@ MediaTaskQueue::Runner::Run()
     mQueue->mRunningThread = NS_GetCurrentThread();
     if (mQueue->mTasks.size() == 0) {
       mQueue->mIsRunning = false;
+      mQueue->mShutdownPromise.ResolveIfExists(true, __func__);
       mon.NotifyAll();
       return NS_OK;
     }
@@ -235,6 +241,7 @@ MediaTaskQueue::Runner::Run()
     if (mQueue->mTasks.size() == 0) {
       // No more events to run. Exit the task runner.
       mQueue->mIsRunning = false;
+      mQueue->mShutdownPromise.ResolveIfExists(true, __func__);
       mon.NotifyAll();
       mQueue->mRunningThread = nullptr;
       return NS_OK;
diff --git a/dom/media/MediaTaskQueue.h b/dom/media/MediaTaskQueue.h
index 1027ed56ef1..ce3827b52cf 100644
--- a/dom/media/MediaTaskQueue.h
+++ b/dom/media/MediaTaskQueue.h
@@ -12,6 +12,7 @@
 #include "mozilla/Monitor.h"
 #include "SharedThreadPool.h"
 #include "nsThreadUtils.h"
+#include "MediaPromise.h"
 
 class nsIRunnable;
 
@@ -19,6 +20,8 @@ namespace mozilla {
 
 class SharedThreadPool;
 
+typedef MediaPromise<bool, bool> ShutdownPromise;
+
 // 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.
@@ -50,7 +53,9 @@ public:
   // remain alive at least until all the events are drained, because the Runners
   // hold a strong reference to the task queue, and one of them is always held
   // by the threadpool event queue when the task queue is non-empty.
-  void BeginShutdown();
+  //
+  // The returned promise is resolved when the queue goes empty.
+  nsRefPtr<ShutdownPromise> BeginShutdown();
 
   // Blocks until all task finish executing.
   void AwaitIdle();
@@ -105,6 +110,7 @@ private:
 
   // True if we've started our shutdown process.
   bool mIsShutdown;
+  MediaPromiseHolder<ShutdownPromise> mShutdownPromise;
 
   class MOZ_STACK_CLASS AutoSetFlushing
   {
diff --git a/dom/media/android/AndroidMediaReader.cpp b/dom/media/android/AndroidMediaReader.cpp
index bd2d32ca8f2..cf8c463f1ad 100644
--- a/dom/media/android/AndroidMediaReader.cpp
+++ b/dom/media/android/AndroidMediaReader.cpp
@@ -99,7 +99,8 @@ nsresult AndroidMediaReader::ReadMetadata(MediaInfo* aInfo,
   return NS_OK;
 }
 
-void AndroidMediaReader::Shutdown()
+nsRefPtr<ShutdownPromise>
+AndroidMediaReader::Shutdown()
 {
   ResetDecode();
   if (mPlugin) {
@@ -107,7 +108,7 @@ void AndroidMediaReader::Shutdown()
     mPlugin = nullptr;
   }
 
-  MediaDecoderReader::Shutdown();
+  return MediaDecoderReader::Shutdown();
 }
 
 // Resets all state related to decoding, emptying all buffers etc.
diff --git a/dom/media/android/AndroidMediaReader.h b/dom/media/android/AndroidMediaReader.h
index 90c4c929abe..4738cfa7b6a 100644
--- a/dom/media/android/AndroidMediaReader.h
+++ b/dom/media/android/AndroidMediaReader.h
@@ -71,7 +71,7 @@ public:
                                 MetadataTags** aTags);
   virtual void Seek(int64_t aTime, int64_t aStartTime, int64_t aEndTime, int64_t aCurrentTime);
 
-  virtual void Shutdown() MOZ_OVERRIDE;
+  virtual nsRefPtr<ShutdownPromise> Shutdown() MOZ_OVERRIDE;
 
   class ImageBufferCallback : public MPAPI::BufferCallback {
     typedef mozilla::layers::Image Image;
diff --git a/dom/media/fmp4/MP4Reader.cpp b/dom/media/fmp4/MP4Reader.cpp
index 0482ae5400a..b54a8b80eba 100644
--- a/dom/media/fmp4/MP4Reader.cpp
+++ b/dom/media/fmp4/MP4Reader.cpp
@@ -139,7 +139,7 @@ MP4Reader::~MP4Reader()
   MOZ_COUNT_DTOR(MP4Reader);
 }
 
-void
+nsRefPtr<ShutdownPromise>
 MP4Reader::Shutdown()
 {
   MOZ_ASSERT(GetTaskQueue()->IsCurrentThreadIn());
@@ -172,7 +172,7 @@ MP4Reader::Shutdown()
     mPlatform = nullptr;
   }
 
-  MediaDecoderReader::Shutdown();
+  return MediaDecoderReader::Shutdown();
 }
 
 void
diff --git a/dom/media/fmp4/MP4Reader.h b/dom/media/fmp4/MP4Reader.h
index 0c425a98fad..bead54a72c5 100644
--- a/dom/media/fmp4/MP4Reader.h
+++ b/dom/media/fmp4/MP4Reader.h
@@ -71,7 +71,7 @@ public:
 
   virtual nsresult ResetDecode() MOZ_OVERRIDE;
 
-  virtual void Shutdown() MOZ_OVERRIDE;
+  virtual nsRefPtr<ShutdownPromise> Shutdown() MOZ_OVERRIDE;
 
 private:
 
diff --git a/dom/media/mediasource/MediaSourceDecoder.h b/dom/media/mediasource/MediaSourceDecoder.h
index 4d1f724e470..efb61a0caef 100644
--- a/dom/media/mediasource/MediaSourceDecoder.h
+++ b/dom/media/mediasource/MediaSourceDecoder.h
@@ -11,6 +11,7 @@
 #include "nsCOMPtr.h"
 #include "nsError.h"
 #include "MediaDecoder.h"
+#include "MediaSourceReader.h"
 
 class nsIStreamListener;
 
@@ -18,7 +19,6 @@ namespace mozilla {
 
 class MediaResource;
 class MediaDecoderStateMachine;
-class MediaSourceReader;
 class SourceBufferDecoder;
 class TrackBuffer;
 
@@ -71,6 +71,8 @@ public:
   virtual nsresult SetCDMProxy(CDMProxy* aProxy) MOZ_OVERRIDE;
 #endif
 
+  MediaSourceReader* GetReader() { return mReader; }
+
 private:
   // The owning MediaSource holds a strong reference to this decoder, and
   // calls Attach/DetachMediaSource on this decoder to set and clear
diff --git a/dom/media/mediasource/MediaSourceReader.cpp b/dom/media/mediasource/MediaSourceReader.cpp
index d6770e640e4..269794a840e 100644
--- a/dom/media/mediasource/MediaSourceReader.cpp
+++ b/dom/media/mediasource/MediaSourceReader.cpp
@@ -236,17 +236,35 @@ MediaSourceReader::OnNotDecoded(MediaData::Type aType, NotDecodedReason aReason)
   GetCallback()->OnNotDecoded(aType, WAITING_FOR_DATA);
 }
 
-void
+nsRefPtr<ShutdownPromise>
 MediaSourceReader::Shutdown()
 {
-  MediaDecoderReader::Shutdown();
-  for (uint32_t i = 0; i < mTrackBuffers.Length(); ++i) {
-    mTrackBuffers[i]->Shutdown();
+  MOZ_ASSERT(mMediaSourceShutdownPromise.IsEmpty());
+  nsRefPtr<ShutdownPromise> p = mMediaSourceShutdownPromise.Ensure(__func__);
+
+  ContinueShutdown(true);
+  return p;
+}
+
+void
+MediaSourceReader::ContinueShutdown(bool aSuccess)
+{
+  MOZ_ASSERT(aSuccess);
+  if (mTrackBuffers.Length()) {
+    mTrackBuffers[0]->Shutdown()->Then(GetTaskQueue(), __func__, this,
+                                       &MediaSourceReader::ContinueShutdown,
+                                       &MediaSourceReader::ContinueShutdown);
+    mShutdownTrackBuffers.AppendElement(mTrackBuffers[0]);
+    mTrackBuffers.RemoveElementAt(0);
+    return;
   }
+
   mAudioTrack = nullptr;
   mAudioReader = nullptr;
   mVideoTrack = nullptr;
   mVideoReader = nullptr;
+
+  MediaDecoderReader::Shutdown()->ChainTo(mMediaSourceShutdownPromise.Steal(), __func__);
 }
 
 void
@@ -259,11 +277,12 @@ MediaSourceReader::BreakCycles()
   MOZ_ASSERT(!mAudioReader);
   MOZ_ASSERT(!mVideoTrack);
   MOZ_ASSERT(!mVideoReader);
+  MOZ_ASSERT(!mTrackBuffers.Length());
 
-  for (uint32_t i = 0; i < mTrackBuffers.Length(); ++i) {
-    mTrackBuffers[i]->BreakCycles();
+  for (uint32_t i = 0; i < mShutdownTrackBuffers.Length(); ++i) {
+    mShutdownTrackBuffers[i]->BreakCycles();
   }
-  mTrackBuffers.Clear();
+  mShutdownTrackBuffers.Clear();
 }
 
 already_AddRefed<MediaDecoderReader>
diff --git a/dom/media/mediasource/MediaSourceReader.h b/dom/media/mediasource/MediaSourceReader.h
index fdeb09b21d3..eabc1e93c7a 100644
--- a/dom/media/mediasource/MediaSourceReader.h
+++ b/dom/media/mediasource/MediaSourceReader.h
@@ -97,7 +97,7 @@ public:
   void RemoveTrackBuffer(TrackBuffer* aTrackBuffer);
   void OnTrackBufferConfigured(TrackBuffer* aTrackBuffer, const MediaInfo& aInfo);
 
-  void Shutdown();
+  nsRefPtr<ShutdownPromise> Shutdown() MOZ_OVERRIDE;
 
   virtual void BreakCycles();
 
@@ -135,6 +135,7 @@ private:
   nsRefPtr<MediaDecoderReader> mVideoReader;
 
   nsTArray<nsRefPtr<TrackBuffer>> mTrackBuffers;
+  nsTArray<nsRefPtr<TrackBuffer>> mShutdownTrackBuffers;
   nsTArray<nsRefPtr<TrackBuffer>> mEssentialTrackBuffers;
   nsRefPtr<TrackBuffer> mAudioTrack;
   nsRefPtr<TrackBuffer> mVideoTrack;
@@ -176,6 +177,9 @@ private:
   bool mVideoIsSeeking;
 
   bool mHasEssentialTrackBuffers;
+
+  void ContinueShutdown(bool aSuccess);
+  MediaPromiseHolder<ShutdownPromise> mMediaSourceShutdownPromise;
 #ifdef MOZ_FMP4
   nsRefPtr<SharedDecoderManager> mSharedDecoderManager;
 #endif
diff --git a/dom/media/mediasource/TrackBuffer.cpp b/dom/media/mediasource/TrackBuffer.cpp
index e19dcea290e..73a4030e1f9 100644
--- a/dom/media/mediasource/TrackBuffer.cpp
+++ b/dom/media/mediasource/TrackBuffer.cpp
@@ -96,23 +96,39 @@ private:
   nsAutoTArray<nsRefPtr<SourceBufferDecoder>,2> mDecoders;
 };
 
-void
+nsRefPtr<ShutdownPromise>
 TrackBuffer::Shutdown()
 {
-  // Finish any decoder initialization, which may add to mInitializedDecoders.
-  // Shutdown waits for any pending events, which may require the monitor,
-  // so we must not hold the monitor during this call.
-  mParentDecoder->GetReentrantMonitor().AssertNotCurrentThreadIn();
-  mTaskQueue->BeginShutdown();
-  mTaskQueue->AwaitShutdownAndIdle();
-  mTaskQueue = nullptr;
+  MOZ_ASSERT(mShutdownPromise.IsEmpty());
+  nsRefPtr<ShutdownPromise> p = mShutdownPromise.Ensure(__func__);
 
+  RefPtr<MediaTaskQueue> queue = mTaskQueue;
+  mTaskQueue = nullptr;
+  queue->BeginShutdown()
+       ->Then(mParentDecoder->GetReader()->GetTaskQueue(), __func__, this,
+              &TrackBuffer::ContinueShutdown, &TrackBuffer::ContinueShutdown);
+
+  return p;
+}
+
+void
+TrackBuffer::ContinueShutdown(bool aSuccess)
+{
+  MOZ_ASSERT(aSuccess);
   ReentrantMonitorAutoEnter mon(mParentDecoder->GetReentrantMonitor());
-  for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
-    mDecoders[i]->GetReader()->Shutdown();
+  if (mDecoders.Length()) {
+    mDecoders[0]->GetReader()->Shutdown()
+                ->Then(mParentDecoder->GetReader()->GetTaskQueue(), __func__, this,
+                       &TrackBuffer::ContinueShutdown, &TrackBuffer::ContinueShutdown);
+    mShutdownDecoders.AppendElement(mDecoders[0]);
+    mDecoders.RemoveElementAt(0);
+    return;
   }
+
   mInitializedDecoders.Clear();
   mParentDecoder = nullptr;
+
+  mShutdownPromise.Resolve(true, __func__);
 }
 
 bool
@@ -433,12 +449,13 @@ TrackBuffer::BreakCycles()
 {
   MOZ_ASSERT(NS_IsMainThread());
 
-  for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
-    mDecoders[i]->BreakCycles();
+  for (uint32_t i = 0; i < mShutdownDecoders.Length(); ++i) {
+    mShutdownDecoders[i]->BreakCycles();
   }
-  mDecoders.Clear();
+  mShutdownDecoders.Clear();
 
   // These are cleared in Shutdown()
+  MOZ_ASSERT(!mDecoders.Length());
   MOZ_ASSERT(mInitializedDecoders.IsEmpty());
   MOZ_ASSERT(!mParentDecoder);
 }
diff --git a/dom/media/mediasource/TrackBuffer.h b/dom/media/mediasource/TrackBuffer.h
index 0e4770f1181..ef2ee18dd94 100644
--- a/dom/media/mediasource/TrackBuffer.h
+++ b/dom/media/mediasource/TrackBuffer.h
@@ -8,6 +8,7 @@
 #define MOZILLA_TRACKBUFFER_H_
 
 #include "SourceBufferDecoder.h"
+#include "MediaPromise.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/mozalloc.h"
@@ -33,7 +34,7 @@ public:
 
   TrackBuffer(MediaSourceDecoder* aParentDecoder, const nsACString& aType);
 
-  void Shutdown();
+  nsRefPtr<ShutdownPromise> Shutdown();
 
   // Append data to the current decoder.  Also responsible for calling
   // NotifyDataArrived on the decoder to keep buffered range computation up
@@ -131,6 +132,11 @@ private:
   // mParentDecoder's monitor.
   nsTArray<nsRefPtr<SourceBufferDecoder>> mDecoders;
 
+  // During shutdown, we move decoders from mDecoders to mShutdownDecoders after
+  // invoking Shutdown. This is all so that we can avoid destroying the decoders
+  // off-main-thread. :-(
+  nsTArray<nsRefPtr<SourceBufferDecoder>> mShutdownDecoders;
+
   // Contains only the initialized decoders managed by this TrackBuffer.
   // Access protected by mParentDecoder's monitor.
   nsTArray<nsRefPtr<SourceBufferDecoder>> mInitializedDecoders;
@@ -153,6 +159,9 @@ private:
   // Set when the first decoder used by this TrackBuffer is initialized.
   // Protected by mParentDecoder's monitor.
   MediaInfo mInfo;
+
+  void ContinueShutdown(bool aSuccess);
+  MediaPromiseHolder<ShutdownPromise> mShutdownPromise;
 };
 
 } // namespace mozilla
diff --git a/dom/media/mediasource/moz.build b/dom/media/mediasource/moz.build
index 1bf57102a45..4365bc99190 100644
--- a/dom/media/mediasource/moz.build
+++ b/dom/media/mediasource/moz.build
@@ -8,6 +8,7 @@ MOCHITEST_MANIFESTS += ['test/mochitest.ini']
 EXPORTS += [
     'AsyncEventRunner.h',
     'MediaSourceDecoder.h',
+    'MediaSourceReader.h',
 ]
 
 EXPORTS.mozilla.dom += [
diff --git a/dom/media/omx/MediaCodecReader.cpp b/dom/media/omx/MediaCodecReader.cpp
index 634a62ab198..c78b7c19fe1 100644
--- a/dom/media/omx/MediaCodecReader.cpp
+++ b/dom/media/omx/MediaCodecReader.cpp
@@ -344,11 +344,11 @@ MediaCodecReader::ReleaseMediaResources()
   ReleaseCriticalResources();
 }
 
-void
+nsRefPtr<ShutdownPromise>
 MediaCodecReader::Shutdown()
 {
   ReleaseResources();
-  MediaDecoderReader::Shutdown();
+  return MediaDecoderReader::Shutdown();
 }
 
 void
diff --git a/dom/media/omx/MediaCodecReader.h b/dom/media/omx/MediaCodecReader.h
index 3f51e34da08..b82531058e4 100644
--- a/dom/media/omx/MediaCodecReader.h
+++ b/dom/media/omx/MediaCodecReader.h
@@ -68,7 +68,7 @@ public:
   // Destroys the decoding state. The reader cannot be made usable again.
   // This is different from ReleaseMediaResources() as Shutdown() is
   // irreversible, whereas ReleaseMediaResources() is reversible.
-  virtual void Shutdown();
+  virtual nsRefPtr<ShutdownPromise> Shutdown();
 
   // Used to retrieve some special information that can only be retrieved after
   // all contents have been continuously parsed. (ex. total duration of some
diff --git a/dom/media/omx/MediaOmxReader.cpp b/dom/media/omx/MediaOmxReader.cpp
index 309d11d4f68..4d9b69177a7 100644
--- a/dom/media/omx/MediaOmxReader.cpp
+++ b/dom/media/omx/MediaOmxReader.cpp
@@ -175,17 +175,20 @@ void MediaOmxReader::ReleaseDecoder()
   mOmxDecoder.clear();
 }
 
-void MediaOmxReader::Shutdown()
+nsRefPtr<ShutdownPromise>
+MediaOmxReader::Shutdown()
 {
   nsCOMPtr<nsIRunnable> cancelEvent =
     NS_NewRunnableMethod(this, &MediaOmxReader::CancelProcessCachedData);
   NS_DispatchToMainThread(cancelEvent);
 
-  MediaDecoderReader::Shutdown();
+  nsRefPtr<ShutdownPromise> p = MediaDecoderReader::Shutdown();
 
   nsCOMPtr<nsIRunnable> event =
     NS_NewRunnableMethod(this, &MediaOmxReader::ReleaseDecoder);
   NS_DispatchToMainThread(event);
+
+  return p;
 }
 
 bool MediaOmxReader::IsWaitingMediaResources()
diff --git a/dom/media/omx/MediaOmxReader.h b/dom/media/omx/MediaOmxReader.h
index 0a0d6719235..cbe88c09c72 100644
--- a/dom/media/omx/MediaOmxReader.h
+++ b/dom/media/omx/MediaOmxReader.h
@@ -104,7 +104,7 @@ public:
 
   virtual void SetIdle() MOZ_OVERRIDE;
 
-  virtual void Shutdown() MOZ_OVERRIDE;
+  virtual nsRefPtr<ShutdownPromise> Shutdown() MOZ_OVERRIDE;
 
   bool IsShutdown() {
     MutexAutoLock lock(mMutex);
diff --git a/dom/media/webm/WebMReader.cpp b/dom/media/webm/WebMReader.cpp
index 5b47c331a1e..e9c3bdac1ea 100644
--- a/dom/media/webm/WebMReader.cpp
+++ b/dom/media/webm/WebMReader.cpp
@@ -218,7 +218,8 @@ WebMReader::~WebMReader()
   MOZ_COUNT_DTOR(WebMReader);
 }
 
-void WebMReader::Shutdown()
+nsRefPtr<ShutdownPromise>
+WebMReader::Shutdown()
 {
 #if defined(MOZ_PDM_VPX)
   if (mVideoTaskQueue) {
@@ -232,7 +233,7 @@ void WebMReader::Shutdown()
     mVideoDecoder = nullptr;
   }
 
-  MediaDecoderReader::Shutdown();
+  return MediaDecoderReader::Shutdown();
 }
 
 nsresult WebMReader::Init(MediaDecoderReader* aCloneDonor)
diff --git a/dom/media/webm/WebMReader.h b/dom/media/webm/WebMReader.h
index 2e19bc8f0b0..94b4f5d42d1 100644
--- a/dom/media/webm/WebMReader.h
+++ b/dom/media/webm/WebMReader.h
@@ -133,7 +133,7 @@ protected:
   ~WebMReader();
 
 public:
-  virtual void Shutdown() MOZ_OVERRIDE;
+  virtual nsRefPtr<ShutdownPromise> Shutdown() MOZ_OVERRIDE;
   virtual nsresult Init(MediaDecoderReader* aCloneDonor);
   virtual nsresult ResetDecode();
   virtual bool DecodeAudioData();