--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -237,17 +237,16 @@ MediaDecoderStateMachine::MediaDecoderSt
   mIsVideoPrerolling(false),
   mAudioCaptured(false),
   INIT_WATCHABLE(mAudioCompleted, false),
   INIT_WATCHABLE(mVideoCompleted, false),
   mNotifyMetadataBeforeFirstFrame(false),
   mQuickBuffering(false),
   mMinimizePreroll(false),
   mDecodeThreadWaiting(false),
-  mDecodingFirstFrame(true),
   mSentLoadedMetadataEvent(false),
   mSentFirstFrameLoadedEvent(false),
   mSentPlaybackEndedEvent(false),
   mVideoDecodeSuspended(false),
   mVideoDecodeSuspendTimer(mTaskQueue),
   mOutputStreamManager(new OutputStreamManager()),
   mResource(aDecoder->GetResource()),
   mAudioOffloading(false),
@@ -1073,17 +1072,16 @@ MediaDecoderStateMachine::ExitState(Stat
 }
 
 void
 MediaDecoderStateMachine::EnterState(State aState)
 {
   MOZ_ASSERT(OnTaskQueue());
   switch (aState) {
     case DECODER_STATE_DECODING_METADATA:
-      mDecodingFirstFrame = true;
       ReadMetadata();
       break;
     case DECODER_STATE_DORMANT:
       DiscardSeekTaskIfExist();
       if (IsPlaying()) {
         StopPlayback();
       }
       Reset();
@@ -2066,22 +2064,16 @@ MediaDecoderStateMachine::EnqueueFirstFr
                              : MediaDecoderEventVisibility::Observable;
       self->mFirstFrameLoadedEvent.Notify(
         nsAutoPtr<MediaInfo>(new MediaInfo(self->mInfo)), visibility);
     },
     // Reject
     []() { MOZ_CRASH("Should not reach"); }));
 }
 
-bool
-MediaDecoderStateMachine::IsDecodingFirstFrame()
-{
-  return mState == DECODER_STATE_DECODING && mDecodingFirstFrame;
-}
-
 void
 MediaDecoderStateMachine::FinishDecodeFirstFrame()
 {
   MOZ_ASSERT(OnTaskQueue());
   DECODER_LOG("FinishDecodeFirstFrame");
 
   if (!mSentFirstFrameLoadedEvent) {
     mMediaSink->Redraw(mInfo.mVideo);
@@ -2098,19 +2090,18 @@ MediaDecoderStateMachine::FinishDecodeFi
 
   // Get potentially updated metadata
   mReader->ReadUpdatedMetadata(&mInfo);
 
   if (!mNotifyMetadataBeforeFirstFrame) {
     // If we didn't have duration and/or start time before, we should now.
     EnqueueLoadedMetadataEvent();
   }
+
   EnqueueFirstFrameLoadedEvent();
-
-  mDecodingFirstFrame = false;
 }
 
 void
 MediaDecoderStateMachine::SeekCompleted()
 {
   MOZ_ASSERT(OnTaskQueue());
   MOZ_ASSERT(mState == DECODER_STATE_SEEKING);
 
@@ -2823,22 +2814,22 @@ MediaDecoderStateMachine::DumpDebugInfo(
   MOZ_ASSERT(NS_IsMainThread());
 
   // It is fine to capture a raw pointer here because MediaDecoder only call
   // this function before shutdown begins.
   nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction([this] () {
     mMediaSink->DumpDebugInfo();
     DUMP_LOG(
       "GetMediaTime=%lld GetClock=%lld mMediaSink=%p "
-      "mState=%s mPlayState=%d mDecodingFirstFrame=%d IsPlaying=%d "
+      "mState=%s mPlayState=%d mSentFirstFrameLoadedEvent=%d IsPlaying=%d "
       "mAudioStatus=%s mVideoStatus=%s mDecodedAudioEndTime=%lld mDecodedVideoEndTime=%lld "
       "mIsAudioPrerolling=%d mIsVideoPrerolling=%d "
       "mAudioCompleted=%d mVideoCompleted=%d",
       GetMediaTime(), mMediaSink->IsStarted() ? GetClock() : -1, mMediaSink.get(),
-      ToStateStr(), mPlayState.Ref(), mDecodingFirstFrame, IsPlaying(),
+      ToStateStr(), mPlayState.Ref(), mSentFirstFrameLoadedEvent, IsPlaying(),
       AudioRequestStatus(), VideoRequestStatus(), mDecodedAudioEndTime, mDecodedVideoEndTime,
       mIsAudioPrerolling, mIsVideoPrerolling, mAudioCompleted.Ref(), mVideoCompleted.Ref());
   });
 
   OwnerThread()->DispatchStateChange(r.forget());
 }
 
 void MediaDecoderStateMachine::AddOutputStream(ProcessedMediaStream* aStream,

--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -562,18 +562,17 @@ protected:
   void OnMetadataRead(MetadataHolder* aMetadata);
   void OnMetadataNotRead(ReadMetadataFailureReason aReason);
 
   // Checks whether we're finished decoding first audio and/or video packets.
   // If so will trigger firing loadeddata event.
   // If there are any queued seek, will change state to DECODER_STATE_SEEKING
   // and return true.
   bool MaybeFinishDecodeFirstFrame();
-  // Return true if we are currently decoding the first frames.
-  bool IsDecodingFirstFrame();
+
   void FinishDecodeFirstFrame();
 
   // Completes the seek operation, moves onto the next appropriate state.
   void SeekCompleted();
 
   // Queries our state to see whether the decode has finished for all streams.
   bool CheckIfDecodeComplete();
 
@@ -880,20 +879,16 @@ private:
 
   nsAutoPtr<MetadataTags> mMetadataTags;
 
   mozilla::MediaMetadataManager mMetadataManager;
 
   // Track our request to update the buffered ranges
   MozPromiseRequestHolder<MediaDecoderReader::BufferedUpdatePromise> mBufferedUpdateRequest;
 
-  // True if we need to call FinishDecodeFirstFrame() upon frame decoding
-  // succeeding.
-  bool mDecodingFirstFrame;
-
   // True if we are back from DECODER_STATE_DORMANT state and
   // LoadedMetadataEvent was already sent.
   bool mSentLoadedMetadataEvent;
 
   // True if we've decoded first frames (thus having the start time) and
   // notified the FirstFrameLoaded event. Note we can't initiate seek until the
   // start time is known which happens when the first frames are decoded or we
   // are playing an MSE stream (the start time is always assumed 0).