Fix getUserMedia so that failure is reported for invalid audio sources.

chrome/renderer/media/cast_receiver_audio_valve.h

 // Copyright 2015 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.
 
 #ifndef CHROME_RENDERER_MEDIA_CAST_RECEIVER_AUDIO_VALVE_H_
 #define CHROME_RENDERER_MEDIA_CAST_RECEIVER_AUDIO_VALVE_H_
 
 #include "base/synchronization/lock.h"
 #include "base/time/time.h"
 #include "media/base/audio_capturer_source.h"
@@ skipping 13 matching lines @@
     public base::RefCountedThreadSafe<CastReceiverAudioValve> {
  public:
   CastReceiverAudioValve(const media::AudioParameters& params,
                          media::AudioCapturerSource::CaptureCallback* cb);
 
   // Called on an unknown thread to provide more decoded audio data from the
   // Cast Receiver.
   void DeliverDecodedAudio(const media::AudioBus* audio_bus,
                            base::TimeTicks playout_time);
 
+  // Called to indicate that audio has started streaming and our capture
+  // callback should be notified.
+  void OnStarted();
+
   // When this returns, no more calls will be forwarded to |cb|.
   void Stop();
 
  private:
   friend class base::RefCountedThreadSafe<CastReceiverAudioValve>;
 
   ~CastReceiverAudioValve();
 
   // Called by AudioPushFifo zero or more times during the call to Capture().
   // Delivers audio data in the required buffer size to |cb_|.
   void DeliverRebufferedAudio(const media::AudioBus& audio_bus,
                               int frame_delay);
 
   media::AudioCapturerSource::CaptureCallback* cb_;
   base::Lock lock_;
 
   media::AudioPushFifo fifo_;
   const int sample_rate_;
 
   // Used to pass the current playout time between DeliverDecodedAudio() and
   // DeviliverRebufferedAudio().
   base::TimeTicks current_playout_time_;
 };
 
 #endif  // CHROME_RENDERER_MEDIA_CAST_RECEIVER_AUDIO_VALVE_H_