Propagate muted state from MediaStreamAudioSource into JS.

media/audio/fake_audio_input_stream.h

Index: media/audio/fake_audio_input_stream.h
diff --git a/media/audio/fake_audio_input_stream.h b/media/audio/fake_audio_input_stream.h
index d9b186a844a9b97d3d3390d6787db2aca3f01f6c..438a3b97e07ee6bc2cdb4720c2df8d3be1c287a3 100644
--- a/media/audio/fake_audio_input_stream.h
+++ b/media/audio/fake_audio_input_stream.h
@@ -54,6 +54,10 @@ class MEDIA_EXPORT FakeAudioInputStream
   // input stream.
   static void BeepOnce();
 
+  // Set the muted state for _all_ FakeAudioInputStreams. The value is global,
+  // so it can be set before any FakeAudioInputStreams have been created.
+  static void SetMutedState(bool is_muted);

[Guido Urdaneta, 2017/06/08 14:15:06]

nit: Change the name to SetGlobalMutedState or similar to make intent clearer.

You could also have the global variable represent the initial/default muted
state, and provide a nonstatic SetMutedState method to change it per stream.
This would allow future code to manupulate the muted state of different streams
independently. WDYT?

[ossu-chromium, 2017/06/08 14:52:08]

Yes, that makes sense.
I could do that, but I haven't the first clue on how to get the AudioInputStream
for a specific Track or something in JavaScript. The current usage also vibes
quite well with how this is implemented in real life, where there's a global
volume/mute setting for the microphone, for example. So.. I'd rather avoid doing
that here unless there's pressing need for that functionality. :)

+
  private:
   FakeAudioInputStream(AudioManagerBase* manager,
                        const AudioParameters& params);