bluetooth: Refactor (Add|Remove)Observer impls into BluetoothAdapter.

device/bluetooth/bluetooth_adapter_mac.h

Index: device/bluetooth/bluetooth_adapter_mac.h
diff --git a/device/bluetooth/bluetooth_adapter_mac.h b/device/bluetooth/bluetooth_adapter_mac.h
index bca4389e95763f9a69e0442d8cefd9160d65e404..3567e0f00cf074f25cd70c6cabc360b862c11c39 100644
--- a/device/bluetooth/bluetooth_adapter_mac.h
+++ b/device/bluetooth/bluetooth_adapter_mac.h
@@ -41,8 +41,6 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterMac
   static base::WeakPtr<BluetoothAdapter> CreateAdapter();
 
   // BluetoothAdapter:
-  void AddObserver(BluetoothAdapter::Observer* observer) override;
-  void RemoveObserver(BluetoothAdapter::Observer* observer) override;
   std::string GetAddress() const override;
   std::string GetName() const override;
   void SetName(const std::string& name,
@@ -129,9 +127,6 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterMac
 
   scoped_refptr<base::SequencedTaskRunner> ui_task_runner_;
 
-  // List of observers interested in event notifications from us.
-  ObserverList<BluetoothAdapter::Observer> observers_;
-
   base::WeakPtrFactory<BluetoothAdapterMac> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BluetoothAdapterMac);