--- a/dom/media/mediasource/MediaSource.cpp
+++ b/dom/media/mediasource/MediaSource.cpp
@@ -518,17 +518,17 @@ MediaSource::DispatchSimpleEvent(const c
   DispatchTrustedEvent(NS_ConvertUTF8toUTF16(aName));
 }
 
 void
 MediaSource::QueueAsyncSimpleEvent(const char* aName)
 {
   MSE_DEBUG("Queuing event '%s'", aName);
   nsCOMPtr<nsIRunnable> event = new AsyncEventRunner<MediaSource>(this, aName);
-  NS_DispatchToMainThread(event);
+  mAbstractMainThread->Dispatch(event.forget());
 }
 
 void
 MediaSource::DurationChange(double aNewDuration, ErrorResult& aRv)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MSE_DEBUG("DurationChange(aNewDuration=%f)", aNewDuration);
 

--- a/dom/media/mediasource/SourceBuffer.cpp
+++ b/dom/media/mediasource/SourceBuffer.cpp
@@ -354,17 +354,17 @@ SourceBuffer::DispatchSimpleEvent(const 
   DispatchTrustedEvent(NS_ConvertUTF8toUTF16(aName));
 }
 
 void
 SourceBuffer::QueueAsyncSimpleEvent(const char* aName)
 {
   MSE_DEBUG("Queuing event '%s'", aName);
   nsCOMPtr<nsIRunnable> event = new AsyncEventRunner<SourceBuffer>(this, aName);
-  NS_DispatchToMainThread(event, NS_DISPATCH_NORMAL);
+  mAbstractMainThread->Dispatch(event.forget());
 }
 
 void
 SourceBuffer::StartUpdating()
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(!mUpdating);
   mUpdating = true;

--- a/dom/media/mediasource/SourceBufferList.cpp
+++ b/dom/media/mediasource/SourceBufferList.cpp
@@ -158,22 +158,23 @@ SourceBufferList::DispatchSimpleEvent(co
   DispatchTrustedEvent(NS_ConvertUTF8toUTF16(aName));
 }
 
 void
 SourceBufferList::QueueAsyncSimpleEvent(const char* aName)
 {
   MSE_DEBUG("Queue event '%s'", aName);
   nsCOMPtr<nsIRunnable> event = new AsyncEventRunner<SourceBufferList>(this, aName);
-  NS_DispatchToMainThread(event);
+  mAbstractMainThread->Dispatch(event.forget());
 }
 
 SourceBufferList::SourceBufferList(MediaSource* aMediaSource)
   : DOMEventTargetHelper(aMediaSource->GetParentObject())
   , mMediaSource(aMediaSource)
+  , mAbstractMainThread(mMediaSource->AbstractMainThread())
 {
   MOZ_ASSERT(aMediaSource);
 }
 
 MediaSource*
 SourceBufferList::GetParentObject() const
 {
   return mMediaSource;

--- a/dom/media/mediasource/SourceBufferList.h
+++ b/dom/media/mediasource/SourceBufferList.h
@@ -92,15 +92,16 @@ private:
   ~SourceBufferList();
 
   friend class AsyncEventRunner<SourceBufferList>;
   void DispatchSimpleEvent(const char* aName);
   void QueueAsyncSimpleEvent(const char* aName);
 
   RefPtr<MediaSource> mMediaSource;
   nsTArray<RefPtr<SourceBuffer> > mSourceBuffers;
+  const RefPtr<AbstractThread> mAbstractMainThread;
 };
 
 } // namespace dom
 
 } // namespace mozilla
 
 #endif /* mozilla_dom_SourceBufferList_h_ */

--- a/dom/media/mediasource/TrackBuffersManager.cpp
+++ b/dom/media/mediasource/TrackBuffersManager.cpp
@@ -1086,19 +1086,20 @@ TrackBuffersManager::OnDemuxerInitDone(n
     mAudioTracks.mLastInfo = new TrackInfoSharedPtr(info.mAudio, streamID);
     mVideoTracks.mLastInfo = new TrackInfoSharedPtr(info.mVideo, streamID);
   }
 
   UniquePtr<EncryptionInfo> crypto = mInputDemuxer->GetCrypto();
   if (crypto && crypto->IsEncrypted()) {
     // Try and dispatch 'encrypted'. Won't go if ready state still HAVE_NOTHING.
     for (uint32_t i = 0; i < crypto->mInitDatas.Length(); i++) {
-      NS_DispatchToMainThread(
+      nsCOMPtr<nsIRunnable> r =
         new DispatchKeyNeededEvent(mParentDecoder, crypto->mInitDatas[i].mInitData,
-                                   crypto->mInitDatas[i].mType));
+                                   crypto->mInitDatas[i].mType);
+      mAbstractMainThread->Dispatch(r.forget());
     }
     info.mCrypto = *crypto;
     // We clear our crypto init data array, so the MediaFormatReader will
     // not emit an encrypted event for the same init data again.
     info.mCrypto.mInitDatas.Clear();
   }
 
   {