MediaRecorder: make sure ondataavailable+onstop events are fired before onerror

content/renderer/media/recorder/media_recorder_handler.h

Index: content/renderer/media/recorder/media_recorder_handler.h
diff --git a/content/renderer/media/recorder/media_recorder_handler.h b/content/renderer/media/recorder/media_recorder_handler.h
index 58d3d6ffc6382ef8f2817a4b80306ba9a7594ee0..e3522171c0e4745cb7dcbd68f0475d4737f3a514 100644
--- a/content/renderer/media/recorder/media_recorder_handler.h
+++ b/content/renderer/media/recorder/media_recorder_handler.h
@@ -74,6 +74,9 @@ class CONTENT_EXPORT MediaRecorderHandler final
                       base::TimeTicks timestamp);
   void WriteData(base::StringPiece data);
 
+  // Updates |media_stream_num_tracks_| and returns true if it has changed.
+  bool CheckAndUpdateAmountOfTracks();
+
   void OnVideoFrameForTesting(const scoped_refptr<media::VideoFrame>& frame,
                               const base::TimeTicks& timestamp);
   void OnAudioBusForTesting(const media::AudioBus& audio_bus,
@@ -98,6 +101,7 @@ class CONTENT_EXPORT MediaRecorderHandler final
 
   bool recording_;
   blink::WebMediaStream media_stream_;  // The MediaStream being recorded.
+  size_t media_stream_num_tracks_;
 
   // |client_| is a weak pointer, and is valid for the lifetime of this object.
   blink::WebMediaRecorderHandlerClient* client_;