arc: bluetooth: Add/Remove BT observer only when ARC is ready

components/arc/bluetooth/arc_bluetooth_bridge.h

 // Copyright 2016 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 COMPONENTS_ARC_BLUETOOTH_ARC_BLUETOOTH_BRIDGE_H_
 #define COMPONENTS_ARC_BLUETOOTH_ARC_BLUETOOTH_BRIDGE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 27 matching lines @@
       public device::BluetoothAdapter::Observer,
       public device::BluetoothAdapterFactory::AdapterCallback,
       public device::BluetoothLocalGattService::Delegate,
       public mojom::BluetoothHost {
  public:
   explicit ArcBluetoothBridge(ArcBridgeService* bridge_service);
   ~ArcBluetoothBridge() override;
 
   // Overridden from InstanceHolder<mojom::BluetoothInstance>::Observer:
   void OnInstanceReady() override;
+  void OnInstanceClosed() override;
 
   void OnAdapterInitialized(scoped_refptr<device::BluetoothAdapter> adapter);
 
   // Overridden from device::BluetoothAdadpter::Observer
   void AdapterPoweredChanged(device::BluetoothAdapter* adapter,
                              bool powered) override;
 
   void DeviceAdded(device::BluetoothAdapter* adapter,
                    device::BluetoothDevice* device) override;
 
@@ skipping 324 matching lines @@
 
   // WeakPtrFactory to use for callbacks.
   base::WeakPtrFactory<ArcBluetoothBridge> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcBluetoothBridge);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_BLUETOOTH_ARC_BLUETOOTH_BRIDGE_H_