Implement mapping blink track id to demuxer streams

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index de61ecb85ed644a2748d82eafc1ff6c6e4713aef..1943c5de84cf7037e75445e40cb086e63fc67595 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -128,6 +128,12 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   bool hasVideo() const override;
   bool hasAudio() const override;
 
+  void enabledAudioTracksChanged(
+      const blink::WebVector<blink::WebMediaPlayer::TrackId>& enabledTrackIds)
+      override;
+  void selectedVideoTrackChanged(
+      blink::WebMediaPlayer::TrackId* selectedTrackId) override;
+
   // Dimensions of the video.
   blink::WebSize naturalSize() const override;