--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -1962,17 +1962,17 @@ MediaDecoderStateMachine::EnsureAudioDec
 {
   AssertCurrentThreadInMonitor();
   NS_ASSERTION(OnStateMachineThread() || OnDecodeThread(),
                "Should be on state machine or decode thread.");
 
   SAMPLE_LOG("EnsureAudioDecodeTaskQueued isDecoding=%d status=%d",
               IsAudioDecoding(), mAudioRequestStatus);
 
-  if (mState >= DECODER_STATE_COMPLETED) {
+  if (mState >= DECODER_STATE_COMPLETED || mState == DECODER_STATE_DORMANT) {
     return NS_OK;
   }
 
   MOZ_ASSERT(mState >= DECODER_STATE_DECODING_FIRSTFRAME);
 
   if (IsAudioDecoding() && mAudioRequestStatus == RequestStatus::Idle && !mWaitingForDecoderSeek) {
     RefPtr<nsIRunnable> task(
       NS_NewRunnableMethod(this, &MediaDecoderStateMachine::DecodeAudio));
@@ -2007,17 +2007,17 @@ MediaDecoderStateMachine::EnsureVideoDec
   AssertCurrentThreadInMonitor();
 
   SAMPLE_LOG("EnsureVideoDecodeTaskQueued isDecoding=%d status=%d",
              IsVideoDecoding(), mVideoRequestStatus);
 
   NS_ASSERTION(OnStateMachineThread() || OnDecodeThread(),
                "Should be on state machine or decode thread.");
 
-  if (mState >= DECODER_STATE_COMPLETED) {
+  if (mState >= DECODER_STATE_COMPLETED || mState == DECODER_STATE_DORMANT) {
     return NS_OK;
   }
 
   MOZ_ASSERT(mState >= DECODER_STATE_DECODING_FIRSTFRAME);
 
   if (IsVideoDecoding() && mVideoRequestStatus == RequestStatus::Idle && !mWaitingForDecoderSeek) {
     RefPtr<nsIRunnable> task(
       NS_NewRunnableMethod(this, &MediaDecoderStateMachine::DecodeVideo));
@@ -2761,22 +2761,20 @@ nsresult MediaDecoderStateMachine::RunSt
       if (IsPlaying()) {
         StopPlayback();
       }
       StopAudioThread();
       FlushDecoding();
       // Now that those threads are stopped, there's no possibility of
       // mPendingWakeDecoder being needed again. Revoke it.
       mPendingWakeDecoder = nullptr;
-      {
-        ReentrantMonitorAutoExit exitMon(mDecoder->GetReentrantMonitor());
-        // Wait for the thread decoding, if any, to exit.
-        DecodeTaskQueue()->AwaitIdle();
-        mReader->ReleaseMediaResources();
-      }
+      DebugOnly<nsresult> rv = DecodeTaskQueue()->Dispatch(
+        NS_NewRunnableMethod(mReader, &MediaDecoderReader::ReleaseMediaResources));
+      MOZ_ASSERT(NS_SUCCEEDED(rv));
+
       return NS_OK;
     }
 
     case DECODER_STATE_WAIT_FOR_RESOURCES: {
       return NS_OK;
     }
 
     case DECODER_STATE_DECODING_NONE: {