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

content/renderer/media/local_media_stream_audio_source.cc

Index: content/renderer/media/local_media_stream_audio_source.cc
diff --git a/content/renderer/media/local_media_stream_audio_source.cc b/content/renderer/media/local_media_stream_audio_source.cc
index 03353f16b3c3d25e7bb1e2ce5430e46d9140158c..5e56aa357dd37e2e4d7c445ee58a23ad5451d482 100644
--- a/content/renderer/media/local_media_stream_audio_source.cc
+++ b/content/renderer/media/local_media_stream_audio_source.cc
@@ -12,9 +12,11 @@ namespace content {
 
 LocalMediaStreamAudioSource::LocalMediaStreamAudioSource(
     int consumer_render_frame_id,
-    const StreamDeviceInfo& device_info)
+    const StreamDeviceInfo& device_info,
+    const ConstraintsCallback& started_callback)
     : MediaStreamAudioSource(true /* is_local_source */),
-      consumer_render_frame_id_(consumer_render_frame_id) {
+      consumer_render_frame_id_(consumer_render_frame_id),
+      started_callback_(started_callback) {
   DVLOG(1) << "LocalMediaStreamAudioSource::LocalMediaStreamAudioSource()";
   MediaStreamSource::SetDeviceInfo(device_info);
 
@@ -84,6 +86,10 @@ void LocalMediaStreamAudioSource::EnsureSourceIsStopped() {
           << GetAudioParameters().AsHumanReadableString() << "}.";
 }
 
+void LocalMediaStreamAudioSource::OnCaptureStarted() {
+  started_callback_.Run(this, MEDIA_DEVICE_OK, "");
+}
+
 void LocalMediaStreamAudioSource::Capture(const media::AudioBus* audio_bus,
                                           int audio_delay_milliseconds,
                                           double volume,