Allow muting/unmuting audio through media track API

media/blink/websourcebuffer_impl.cc

Index: media/blink/websourcebuffer_impl.cc
diff --git a/media/blink/websourcebuffer_impl.cc b/media/blink/websourcebuffer_impl.cc
index 9386f5222eca6a9145c7f5e53e6853ebebfa37ca..dab5c7a803260bfa224060a2ee4480b731b6b0bf 100644
--- a/media/blink/websourcebuffer_impl.cc
+++ b/media/blink/websourcebuffer_impl.cc
@@ -189,6 +189,11 @@ void WebSourceBufferImpl::InitSegmentReceived(scoped_ptr<MediaTracks> tracks) {
 
   std::vector<blink::WebMediaPlayer::TrackId> blinkTrackIds =
       client_->initializationSegmentReceived(trackInfoVector);
+
+  DCHECK_EQ(blinkTrackIds.size(), tracks->tracks().size());
+  for (size_t i = 0; i < blinkTrackIds.size(); ++i) {
+    demuxer_->OnTrackIdAssigned(blinkTrackIds[i], tracks->tracks()[i].get());
+  }
 }
 
 }  // namespace media