Bug 1344772 - set a dirty flag so we can process the notification later. r=jya

https://hg.mozilla.org/mozilla-central/file/34c6c2f302e7b48e3ad2cec575cbd34d423a9d32/dom/media/MediaFormatReader.cpp#l2835
NotifyDataArrived() is dispatched again if |mNotifyDataArrivedPromise.Exists()| which will then be dispatched again
recursively until mNotifyDataArrivedPromise is completed. This is a waste of CPU cycles.

We can use a dirty flag to note we should update buffer ranges again when the current update is done.

MozReview-Commit-ID: 6hInhGKnXJE

--HG--
extra : rebase_source : 71aa2c16112428c34def094515e37aa1f028a3fc

dom/media/MediaFormatReader.cpp

@@ -1078,6 +1078,7 @@ MediaFormatReader::MediaFormatReader(AbstractMediaDecoder* aDecoder,
            Preferences::GetUint("media.video-max-decode-error", 2))
   , mDemuxer(new DemuxerProxy(aDemuxer))
   , mDemuxerInitDone(false)
+  , mPendingNotifyDataArrived(false)
   , mLastReportedNumDecodedFrames(0)
   , mPreviousDecodedKeyframeTime_us(sNoPreviousDecodedKeyframe)
   , mInitDone(false)
@@ -2877,10 +2878,8 @@ MediaFormatReader::NotifyDataArrived()
   }
 
   if (mNotifyDataArrivedPromise.Exists()) {
-    // Already one in progress. Reschedule for later.
-    RefPtr<nsIRunnable> task(
-        NewRunnableMethod(this, &MediaFormatReader::NotifyDataArrived));
-    OwnerThread()->Dispatch(task.forget());
+    // Already one in progress. Set the dirty flag so we can process it later.
+    mPendingNotifyDataArrived = true;
     return;
   }
 
@@ -2891,6 +2890,10 @@ MediaFormatReader::NotifyDataArrived()
              self->mNotifyDataArrivedPromise.Complete();
              self->UpdateBuffered();
              self->NotifyTrackDemuxers();
+             if (self->mPendingNotifyDataArrived) {
+               self->mPendingNotifyDataArrived = false;
+               self->NotifyDataArrived();
+             }
            },
            [self]() { self->mNotifyDataArrivedPromise.Complete(); })
     ->Track(mNotifyDataArrivedPromise);

dom/media/MediaFormatReader.h

@@ -450,6 +450,7 @@ private:
   void OnDemuxerInitFailed(const MediaResult& aError);
   MozPromiseRequestHolder<MediaDataDemuxer::InitPromise> mDemuxerInitRequest;
   MozPromiseRequestHolder<NotifyDataArrivedPromise> mNotifyDataArrivedPromise;
+  bool mPendingNotifyDataArrived;
   void OnDemuxFailed(TrackType aTrack, const MediaResult &aError);
 
   void DoDemuxVideo();