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

content/renderer/media/local_media_stream_audio_source.h

Index: content/renderer/media/local_media_stream_audio_source.h
diff --git a/content/renderer/media/local_media_stream_audio_source.h b/content/renderer/media/local_media_stream_audio_source.h
index 1d9d63a0e8d2043c38333e6e5d5a6a077f634cfe..0b92751403771203fb2b43d96a4523f44d5f485a 100644
--- a/content/renderer/media/local_media_stream_audio_source.h
+++ b/content/renderer/media/local_media_stream_audio_source.h
@@ -23,7 +23,8 @@ class CONTENT_EXPORT LocalMediaStreamAudioSource
   // audio data. Audio parameters and (optionally) a pre-existing audio session
   // ID are read from |device_info|.
   LocalMediaStreamAudioSource(int consumer_render_frame_id,
-                              const StreamDeviceInfo& device_info);
+                              const StreamDeviceInfo& device_info,
+                              const ConstraintsCallback& started_callback);
 
   ~LocalMediaStreamAudioSource() final;
 
@@ -33,6 +34,7 @@ class CONTENT_EXPORT LocalMediaStreamAudioSource
   void EnsureSourceIsStopped() final;
 
   // media::AudioCapturerSource::CaptureCallback implementation.
+  void OnCaptureStarted() final;
   void Capture(const media::AudioBus* audio_bus,
                int audio_delay_milliseconds,
                double volume,
@@ -46,6 +48,9 @@ class CONTENT_EXPORT LocalMediaStreamAudioSource
   // The device created by the AudioDeviceFactory in EnsureSourceIsStarted().
   scoped_refptr<media::AudioCapturerSource> source_;
 
+  // Callback that's called when the audio source has been initialized.
+  ConstraintsCallback started_callback_;
+
   // In debug builds, check that all methods that could cause object graph
   // or data flow changes are being called on the main thread.
   base::ThreadChecker thread_checker_;