Caching AudioOutputDevice instances in mixer manager

content/renderer/media/audio_device_factory.cc

Index: content/renderer/media/audio_device_factory.cc
diff --git a/content/renderer/media/audio_device_factory.cc b/content/renderer/media/audio_device_factory.cc
index 40d8455f5c402a2c1a02af593bd174ab333add57..fd0afe5e008072e708f8888d4ca23fd317fad75c 100644
--- a/content/renderer/media/audio_device_factory.cc
+++ b/content/renderer/media/audio_device_factory.cc
@@ -135,22 +135,14 @@ AudioDeviceFactory::NewAudioCapturerSource(int render_frame_id) {
 }
 
 // static
-// TODO(http://crbug.com/587461): Find a better way to check if device exists
-// and is authorized.
 media::OutputDeviceInfo AudioDeviceFactory::GetOutputDeviceInfo(
     int render_frame_id,
     int session_id,
     const std::string& device_id,
     const url::Origin& security_origin) {
-  scoped_refptr<media::AudioRendererSink> sink = NewFinalAudioRendererSink(
+  RenderThreadImpl* render_thread = RenderThreadImpl::current();

[miu, 2016/05/12 21:53:06]

Not sure if this happens in any unit tests, but what if
RenderThreadImpl::current() returns nullptr? Perhaps a DCHECK(render_thread)
should go here (which indicates to any unit test authors that they need to make
sure a RenderThreadImpl is instantiated).

[o1ka, 2016/05/17 17:17:23]

Done.
Now it does not happen in unit tests (and I hope it will never happen because
will be properly mocked). 

+  return render_thread->GetAudioRendererMixerManager()->GetOutputDeviceInfo(
       render_frame_id, session_id, device_id, security_origin);
-
-  const media::OutputDeviceInfo& device_info = sink->GetOutputDeviceInfo();
-
-  // TODO(olka): Cache it and reuse, http://crbug.com/586161
-  sink->Stop();  // Must be stopped.
-
-  return device_info;
 }
 
 AudioDeviceFactory::AudioDeviceFactory() {