Caching AudioOutputDevice instances in mixer manager

content/renderer/media/audio_device_factory.cc

 // Copyright (c) 2012 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.
 
 #include "content/renderer/media/audio_device_factory.h"
 
 #include "base/logging.h"
 #include "content/renderer/media/audio_input_message_filter.h"
 #include "content/renderer/media/audio_message_filter.h"
 #include "content/renderer/media/audio_renderer_mixer_manager.h"
@@ skipping 117 matching lines @@
     if (source)
       return source;
   }
 
   AudioInputMessageFilter* const filter = AudioInputMessageFilter::Get();
   return new media::AudioInputDevice(
       filter->CreateAudioInputIPC(render_frame_id), filter->io_task_runner());
 }
 
 // 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() {
   DCHECK(!factory_) << "Can't register two factories at once.";
   factory_ = this;
 }
 
 AudioDeviceFactory::~AudioDeviceFactory() {
   factory_ = NULL;
 }
@@ skipping 11 matching lines @@
                                                device_id, security_origin);
     if (sink)
       return sink;
   }
 
   return NewOutputDevice(render_frame_id, session_id, device_id,
                          security_origin);
 }
 
 }  // namespace content