Cleanup AudioDeviceThread to reduce locking and unused features.

media/audio/audio_input_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.
 
 // Low-latency audio capturing class utilizing audio input stream provided
 // by a server (browser) process by use of an IPC interface.
 //
 // Relationship of classes:
 //
 //  AudioInputController                 AudioInputDevice
@@ skipping 138 matching lines @@
   // Stores the Automatic Gain Control state. Default is false.
   // Only modified on the IO thread.
   bool agc_is_enabled_;
 
   // 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<AudioInputDevice::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(miu): Replace this by changing AudioCapturerSource to accept the
   // callback via Start(). See http://crbug.com/151051 for details.
   bool stopping_hack_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioInputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_INPUT_DEVICE_H_