Allow muting/unmuting audio through media track API

media/filters/media_source_state.cc

Index: media/filters/media_source_state.cc
diff --git a/media/filters/media_source_state.cc b/media/filters/media_source_state.cc
index 89d488ef21031b58eaf62f692f25f8f738ac2007..3b47b6e58380ab40610957c9aac95641abdf6f0e 100644
--- a/media/filters/media_source_state.cc
+++ b/media/filters/media_source_state.cc
@@ -477,8 +477,22 @@ bool MediaSourceState::OnNewConfigs(
     const StreamParser::TextTrackConfigMap& text_configs) {
   DCHECK(tracks.get());
   media_tracks_ = std::move(tracks);
-  const AudioDecoderConfig& audio_config = media_tracks_->getFirstAudioConfig();
-  const VideoDecoderConfig& video_config = media_tracks_->getFirstVideoConfig();
+
+  const MediaTrack* audio_track = nullptr;
+  const MediaTrack* video_track = nullptr;
+  AudioDecoderConfig audio_config;
+  VideoDecoderConfig video_config;
+  for (const auto& track : media_tracks_->tracks()) {
+    if (!audio_track && track->type() == MediaTrack::Audio &&
+        media_tracks_->getAudioConfig(track->id()).IsValidConfig()) {
+      audio_config = media_tracks_->getAudioConfig(track->id());
+      audio_track = track.get();
+    } else if (!video_track && track->type() == MediaTrack::Video &&
+               media_tracks_->getVideoConfig(track->id()).IsValidConfig()) {
+      video_config = media_tracks_->getVideoConfig(track->id());
+      video_track = track.get();
+    }
+  }
 
   DVLOG(1) << "OnNewConfigs(" << allow_audio << ", " << allow_video << ", "
            << audio_config.IsValidConfig() << ", "
@@ -526,7 +540,8 @@ bool MediaSourceState::OnNewConfigs(
     }
 
     if (!audio_) {
-      audio_ = create_demuxer_stream_cb_.Run(DemuxerStream::AUDIO);
+      DCHECK(audio_track);
+      audio_ = create_demuxer_stream_cb_.Run(*audio_track);
 
       if (!audio_) {
         DVLOG(1) << "Failed to create an audio stream.";
@@ -554,7 +569,8 @@ bool MediaSourceState::OnNewConfigs(
     }
 
     if (!video_) {
-      video_ = create_demuxer_stream_cb_.Run(DemuxerStream::VIDEO);
+      DCHECK(video_track);
+      video_ = create_demuxer_stream_cb_.Run(*video_track);
 
       if (!video_) {
         DVLOG(1) << "Failed to create a video stream.";
@@ -574,8 +590,11 @@ bool MediaSourceState::OnNewConfigs(
   if (text_stream_map_.empty()) {
     for (TextConfigItr itr = text_configs.begin(); itr != text_configs.end();
          ++itr) {
+      // TODO(servolk): Look into unifying text tracks code path with audio and
+      // video track code paths.
+      MediaTrack dummy_text_track(MediaTrack::Text, "", "", "", "");
       ChunkDemuxerStream* const text_stream =
-          create_demuxer_stream_cb_.Run(DemuxerStream::TEXT);
+          create_demuxer_stream_cb_.Run(dummy_text_track);
       if (!frame_processor_->AddTrack(itr->first, text_stream)) {
         success &= false;
         MEDIA_LOG(ERROR, media_log_) << "Failed to add text track ID "