device/bluetooth:Implement Register() for BluetoothAudioSinkChromeOS.

device/bluetooth/bluetooth_adapter_chromeos.h

Index: device/bluetooth/bluetooth_adapter_chromeos.h
diff --git a/device/bluetooth/bluetooth_adapter_chromeos.h b/device/bluetooth/bluetooth_adapter_chromeos.h
index 5ee633f53601ce9d06fd760b4e52a3d6b1582962..bae948d60db2d0b3b1bfafa697c392db79290da9 100644
--- a/device/bluetooth/bluetooth_adapter_chromeos.h
+++ b/device/bluetooth/bluetooth_adapter_chromeos.h
@@ -19,6 +19,7 @@
 #include "dbus/object_path.h"
 #include "device/bluetooth/bluetooth_adapter.h"
 #include "device/bluetooth/bluetooth_audio_sink.h"
+#include "device/bluetooth/bluetooth_audio_sink_chromeos.h"
 #include "device/bluetooth/bluetooth_device.h"
 #include "device/bluetooth/bluetooth_export.h"
 
@@ -28,6 +29,7 @@ class BluetoothSocketThread;
 
 namespace chromeos {
 
+class BluetoothAudioSinkChromeOS;
 class BluetoothChromeOSTest;
 class BluetoothDeviceChromeOS;
 class BluetoothPairingChromeOS;
@@ -182,6 +184,12 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterChromeOS
   void OnRequestDefaultAgentError(const std::string& error_name,
                                   const std::string& error_message);
 
+  // Called by BluetoothAudioSinkChromeOS on completion of registering an audio
+  // sink.
+  void OnRegisterAudioSink(
+      const device::BluetoothAdapter::AcquiredCallback& callback,
+      scoped_refptr<device::BluetoothAudioSink> audio_sink);
+
   // Internal method to obtain a BluetoothPairingChromeOS object for the device
   // with path |object_path|. Returns the existing pairing object if the device
   // already has one (usually an outgoing connection in progress) or a new