--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -1679,29 +1679,26 @@ MediaDecoderStateMachine::MediaDecoderSt
   mFrameStats(&aDecoder->GetFrameStatistics()),
   mVideoFrameContainer(aDecoder->GetVideoFrameContainer()),
   mAudioChannel(aDecoder->GetAudioChannel()),
   mTaskQueue(new TaskQueue(GetMediaThreadPool(MediaThreadType::PLAYBACK),
                            /* aSupportsTailDispatch = */ true)),
   mWatchManager(this, mTaskQueue),
   mDispatchedStateMachine(false),
   mDelayedScheduler(mTaskQueue),
-  INIT_WATCHABLE(mState, DECODER_STATE_DECODING_METADATA),
   mCurrentFrameID(0),
   INIT_WATCHABLE(mObservedDuration, TimeUnit()),
   mFragmentEndTime(-1),
   mReader(new MediaDecoderReaderWrapper(mTaskQueue, aReader)),
   mDecodedAudioEndTime(0),
   mDecodedVideoEndTime(0),
   mPlaybackRate(1.0),
   mLowAudioThresholdUsecs(detail::LOW_AUDIO_USECS),
   mAmpleAudioThresholdUsecs(detail::AMPLE_AUDIO_USECS),
   mAudioCaptured(false),
-  INIT_WATCHABLE(mAudioCompleted, false),
-  INIT_WATCHABLE(mVideoCompleted, false),
   mNotifyMetadataBeforeFirstFrame(false),
   mMinimizePreroll(false),
   mSentLoadedMetadataEvent(false),
   mSentFirstFrameLoadedEvent(false),
   mVideoDecodeSuspended(false),
   mVideoDecodeSuspendTimer(mTaskQueue),
   mOutputStreamManager(new OutputStreamManager()),
   mResource(aDecoder->GetResource()),
@@ -3232,17 +3229,17 @@ MediaDecoderStateMachine::DumpDebugInfo(
     DUMP_LOG(
       "GetMediaTime=%lld GetClock=%lld mMediaSink=%p "
       "mState=%s mPlayState=%d mSentFirstFrameLoadedEvent=%d IsPlaying=%d "
       "mAudioStatus=%s mVideoStatus=%s mDecodedAudioEndTime=%lld mDecodedVideoEndTime=%lld "
       "mAudioCompleted=%d mVideoCompleted=%d",
       GetMediaTime(), mMediaSink->IsStarted() ? GetClock() : -1, mMediaSink.get(),
       ToStateStr(), mPlayState.Ref(), mSentFirstFrameLoadedEvent, IsPlaying(),
       AudioRequestStatus(), VideoRequestStatus(), mDecodedAudioEndTime, mDecodedVideoEndTime,
-      mAudioCompleted.Ref(), mVideoCompleted.Ref());
+      mAudioCompleted, mVideoCompleted);
   });
 
   // Since the task is run asynchronously, it is possible other tasks get first
   // and change the object states before we print them. Therefore we want to
   // dispatch this task immediately without waiting for the tail dispatching
   // phase so object states are less likely to change before being printed.
   OwnerThread()->Dispatch(r.forget(),
     AbstractThread::AssertDispatchSuccess, AbstractThread::TailDispatch);

--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -557,19 +557,17 @@ private:
 
   // Queue of audio frames. This queue is threadsafe, and is accessed from
   // the audio, decoder, state machine, and main threads.
   MediaQueue<MediaData> mAudioQueue;
   // Queue of video frames. This queue is threadsafe, and is accessed from
   // the decoder, state machine, and main threads.
   MediaQueue<MediaData> mVideoQueue;
 
-  // The decoder monitor must be obtained before modifying this state.
-  // Accessed on state machine, audio, main, and AV thread.
-  Watchable<State> mState;
+  State mState = DECODER_STATE_DECODING_METADATA;
 
   UniquePtr<StateObject> mStateObj;
 
   media::TimeUnit Duration() const { MOZ_ASSERT(OnTaskQueue()); return mDuration.Ref().ref(); }
 
   // Recomputes the canonical duration from various sources.
   void RecomputeDuration();
 
@@ -676,27 +674,21 @@ private:
   void OnSuspendTimerResolved();
   void OnSuspendTimerRejected();
 
   // True if we shouldn't play our audio (but still write it to any capturing
   // streams). When this is true, the audio thread will never start again after
   // it has stopped.
   bool mAudioCaptured;
 
-  // True if the audio playback thread has finished. It is finished
-  // when either all the audio frames have completed playing, or we've moved
-  // into shutdown state, and the threads are to be
-  // destroyed. Written by the audio playback thread and read and written by
-  // the state machine thread. Synchronised via decoder monitor.
-  // When data is being sent to a MediaStream, this is true when all data has
-  // been written to the MediaStream.
-  Watchable<bool> mAudioCompleted;
+  // True if all audio frames are already rendered.
+  bool mAudioCompleted = false;
 
   // True if all video frames are already rendered.
-  Watchable<bool> mVideoCompleted;
+  bool mVideoCompleted = false;
 
   // Flag whether we notify metadata before decoding the first frame or after.
   //
   // Note that the odd semantics here are designed to replicate the current
   // behavior where we notify the decoder each time we come out of dormant, but
   // send suppressed event visibility for those cases. This code can probably be
   // simplified.
   bool mNotifyMetadataBeforeFirstFrame;