Update WebmMuxer for audio component of MediaStream recording.

media/capture/webm_muxer.h

Index: media/capture/webm_muxer.h
diff --git a/media/capture/webm_muxer.h b/media/capture/webm_muxer.h
index 7196d1d4f9f33c95b88548ab8ba92dd3589015c1..f349bfa60f919da37049fa5e2087ea5c26575d47 100644
--- a/media/capture/webm_muxer.h
+++ b/media/capture/webm_muxer.h
@@ -21,6 +21,7 @@ class Size;
 namespace media {
 
 class VideoFrame;
+class AudioParameters;
 
 // Adapter class to manage a WebM container [1], a simplified version of a
 // Matroska container [2], composed of an EBML header, and a single Segment
@@ -41,23 +42,32 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
 
   // |codec| can be VP8 or VP9 and should coincide with whatever is sent in
   // OnEncodedVideo().
-  WebmMuxer(VideoCodec codec, const WriteDataCB& write_data_callback);
+  WebmMuxer(VideoCodec codec,
+            size_t num_video_tracks,
+            size_t num_audio_tracks,
+            const WriteDataCB& write_data_callback);
   ~WebmMuxer() override;
 
-  // Adds a |video_frame| with |encoded_data.data()| to WebM Segment.
+  // Functions to add video and audio frames with |encoded_data.data()|
+  // to WebM Segment.
   void OnEncodedVideo(const scoped_refptr<VideoFrame>& video_frame,
                       scoped_ptr<std::string> encoded_data,
                       base::TimeTicks timestamp,
                       bool is_key_frame);
+  void OnEncodedAudio(const media::AudioParameters& params,
+                      scoped_ptr<std::string> encoded_data,
+                      base::TimeTicks timestamp);
 
  private:
   friend class WebmMuxerTest;
 
-  // Creates and adds a new video track. Called upon receiving the first
-  // frame of a given Track, adds |frame_size| and |frame_rate| to the Segment
+  // Methods for creating and adding video and audio tracks, called upon
+  // receiving the first frame of a given Track.
+  // AddVideoTrack adds |frame_size| and |frame_rate| to the Segment
   // info, although individual frames passed to OnEncodedVideo() can have any
   // frame size.
   void AddVideoTrack(const gfx::Size& frame_size, double frame_rate);
+  void AddAudioTrack(const media::AudioParameters& params);
 
   // IMkvWriter interface.
   mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
@@ -73,12 +83,17 @@ class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
   // Video Codec configured: VP9 if true, otherwise VP8 is used by default.
   const bool use_vp9_;
 
-  // A caller-side identifier to interact with |segment_|, initialised upon
-  // first frame arrival by AddVideoTrack().
-  uint64_t track_index_;
+  // Caller-side identifiers to interact with |segment_|, initialised upon
+  // first frame arrival to Add{Video, Audio}Track().
+  uint64_t video_track_index_;
+  uint64_t audio_track_index_;
 
   // Origin of times for frame timestamps.
   base::TimeTicks first_frame_timestamp_;
+  base::TimeDelta most_recent_timestamp_;
+
+  bool has_video_;
+  bool has_audio_;
 
   // Callback to dump written data as being called by libwebm.
   const WriteDataCB write_data_callback_;