Detect AudioInputStream muting and propagate to MediaStreamAudioSource.

content/renderer/media/external_media_stream_audio_source.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/external_media_stream_audio_source.h"
 
 namespace content {
 
 ExternalMediaStreamAudioSource::ExternalMediaStreamAudioSource(
     scoped_refptr<media::AudioCapturerSource> source,
@@ skipping 58 matching lines @@
   MediaStreamAudioSource::DeliverDataToTracks(
       *audio_bus,
       base::TimeTicks::Now() -
           base::TimeDelta::FromMilliseconds(audio_delay_milliseconds));
 }
 
 void ExternalMediaStreamAudioSource::OnCaptureError(const std::string& why) {
   StopSourceOnError(why);
 }
 
+void ExternalMediaStreamAudioSource::OnCaptureMuted(bool is_muted) {
+  SetMutedState(is_muted);
+}
+
 }  // namespace content