Use StreamParser::TrackId instead of string for MediaTrack::byteStreamTrackId

media/base/media_tracks.h

Index: media/base/media_tracks.h
diff --git a/media/base/media_tracks.h b/media/base/media_tracks.h
index 4e0fbb0fc1f88195ce14cc05d14a424924be4d5d..73c2429d09e73573633c31e963d1b7d095b609d9 100644
--- a/media/base/media_tracks.h
+++ b/media/base/media_tracks.h
@@ -28,21 +28,21 @@ class MEDIA_EXPORT MediaTracks {
 
   // Callers need to ensure that track id is unique.
   void AddAudioTrack(const AudioDecoderConfig& config,
-                     const std::string& id,
+                     StreamParser::TrackId id,
                      const std::string& kind,
                      const std::string& label,
                      const std::string& language);
   // Callers need to ensure that track id is unique.
   void AddVideoTrack(const VideoDecoderConfig& config,
-                     const std::string& id,
+                     StreamParser::TrackId id,
                      const std::string& kind,
                      const std::string& label,
                      const std::string& language);
 
   const MediaTracksCollection& tracks() const { return tracks_; }
 
-  const AudioDecoderConfig& getAudioConfig(const std::string& id) const;
-  const VideoDecoderConfig& getVideoConfig(const std::string& id) const;
+  const AudioDecoderConfig& getAudioConfig(StreamParser::TrackId id) const;
+  const VideoDecoderConfig& getVideoConfig(StreamParser::TrackId id) const;
 
   // TODO(servolk): These are temporary helpers useful until all code paths are
   // converted to properly handle multiple media tracks.
@@ -51,8 +51,8 @@ class MEDIA_EXPORT MediaTracks {
 
  private:
   MediaTracksCollection tracks_;
-  std::map<std::string, AudioDecoderConfig> audio_configs_;
-  std::map<std::string, VideoDecoderConfig> video_configs_;
+  std::map<StreamParser::TrackId, AudioDecoderConfig> audio_configs_;
+  std::map<StreamParser::TrackId, VideoDecoderConfig> video_configs_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaTracks);
 };