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

content/renderer/media/webrtc/processed_local_audio_source.cc

Index: content/renderer/media/webrtc/processed_local_audio_source.cc
diff --git a/content/renderer/media/webrtc/processed_local_audio_source.cc b/content/renderer/media/webrtc/processed_local_audio_source.cc
index fa89a2137cf5c8dd2edb57c71449dacf75003fc2..bac130044f25a375c5431adc860ef085ff17c5da 100644
--- a/content/renderer/media/webrtc/processed_local_audio_source.cc
+++ b/content/renderer/media/webrtc/processed_local_audio_source.cc
@@ -29,10 +29,14 @@ void* const kClassIdentifier = const_cast<void**>(&kClassIdentifier);
 ProcessedLocalAudioSource::ProcessedLocalAudioSource(
     int consumer_render_frame_id,
     const StreamDeviceInfo& device_info,
+    const blink::WebMediaConstraints& constraints,
+    const ConstraintsCallback& started_callback,
     PeerConnectionDependencyFactory* factory)
     : MediaStreamAudioSource(true /* is_local_source */),
       consumer_render_frame_id_(consumer_render_frame_id),
       pc_factory_(factory),
+      constraints_(constraints),
+      started_callback_(started_callback),
       volume_(0),
       allow_invalid_render_frame_id_for_testing_(false) {
   DCHECK(pc_factory_);
@@ -53,14 +57,6 @@ ProcessedLocalAudioSource* ProcessedLocalAudioSource::From(
   return nullptr;
 }
 
-void ProcessedLocalAudioSource::SetSourceConstraints(
-    const blink::WebMediaConstraints& constraints) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!constraints.isNull());
-  DCHECK(!source_);
-  constraints_ = constraints;
-}
-
 void* ProcessedLocalAudioSource::GetClassIdentifier() const {
   return kClassIdentifier;
 }
@@ -263,6 +259,10 @@ int ProcessedLocalAudioSource::MaxVolume() const {
   return WebRtcAudioDeviceImpl::kMaxVolumeLevel;
 }
 
+void ProcessedLocalAudioSource::OnCaptureStarted() {
+  started_callback_.Run(this, MEDIA_DEVICE_OK, "");
+}
+
 void ProcessedLocalAudioSource::Capture(const media::AudioBus* audio_bus,
                                         int audio_delay_milliseconds,
                                         double volume,