Cleanup AudioDeviceThread to reduce locking and unused features.

media/audio/audio_output_device.h

 // 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.
 //
 // Audio rendering unit utilizing audio output stream provided by browser
 // process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioOutputController                AudioOutputDevice
@@ skipping 180 matching lines @@
   // If |device_id_| is empty and |session_id_| is not, |matched_device_id_| is
   // received in OnDeviceAuthorized().
   std::string matched_device_id_;
 
   // Our audio thread callback class.  See source file for details.
   class AudioThreadCallback;
 
   // In order to avoid a race between OnStreamCreated and Stop(), we use this
   // guard to control stopping and starting the audio thread.
   base::Lock audio_thread_lock_;
-  AudioDeviceThread audio_thread_;
   std::unique_ptr<AudioOutputDevice::AudioThreadCallback> audio_callback_;
+  std::unique_ptr<AudioDeviceThread> audio_thread_;
 
   // Temporary hack to ignore OnStreamCreated() due to the user calling Stop()
   // so we don't start the audio thread pointing to a potentially freed
   // |callback_|.
   //
   // TODO(scherkus): Replace this by changing AudioRendererSink to either accept
   // the callback via Start(). See http://crbug.com/151051 for details.
   bool stopping_hack_;
 
   base::WaitableEvent did_receive_auth_;
   AudioParameters output_params_;
   OutputDeviceStatus device_status_;
 
   const base::TimeDelta auth_timeout_;
   std::unique_ptr<base::OneShotTimer> auth_timeout_action_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_