device/bluetooth:Implement Register() for BluetoothAudioSinkChromeOS.

device/bluetooth/bluetooth_audio_sink.h

 // Copyright 2014 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.
 
 #ifndef DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_
 
 #include <stdint.h>
 #include <string>
 #include <vector>
@@ skipping 80 matching lines @@
   virtual void AddObserver(Observer* observer) = 0;
   virtual void RemoveObserver(Observer* observer) = 0;
 
   // Getters for state and volume.
   virtual State GetState() const = 0;
   virtual uint16_t GetVolume() const = 0;
 
  protected:
   friend class base::RefCounted<BluetoothAudioSink>;
   BluetoothAudioSink();
+
+  // The destructor should invoke Unregister() to ensure the audio sink will be

[armansito, 2015/01/30 01:27:46]

nit: Say "The destructor invokes Unregister()". Saying it "should" makes it
sound like your guessing :P

[Miao, 2015/01/30 03:59:04]

Done.

+  // unregistered even if the user applications fail to do so.
   virtual ~BluetoothAudioSink();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BluetoothAudioSink);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_AUDIO_SINK_H_