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

components/arc/bluetooth/arc_bluetooth_bridge.h

Index: components/arc/bluetooth/arc_bluetooth_bridge.h
diff --git a/components/arc/bluetooth/arc_bluetooth_bridge.h b/components/arc/bluetooth/arc_bluetooth_bridge.h
index f8b7150c768c09c130b7ecb9306dfe379a473a7b..af7ef294c5590b6f1de0093f8de98c4590b0f303 100644
--- a/components/arc/bluetooth/arc_bluetooth_bridge.h
+++ b/components/arc/bluetooth/arc_bluetooth_bridge.h
@@ -45,6 +45,7 @@ class ArcBluetoothBridge
 
   // Overridden from InstanceHolder<mojom::BluetoothInstance>::Observer:
   void OnInstanceReady() override;
+  void OnInstanceClosed() override;
 
   void OnAdapterInitialized(scoped_refptr<device::BluetoothAdapter> adapter);
 
@@ -364,6 +365,7 @@ class ArcBluetoothBridge
   mojo::Binding<mojom::BluetoothHost> binding_;
 
   scoped_refptr<bluez::BluetoothAdapterBlueZ> bluetooth_adapter_;
+  bool bluetooth_observer_flag_ = false;

[rkc, 2016/08/08 21:58:29]

The correct solution is just to add a HasObserver method to BluetoothAdapter.
Maintaining a flag for this shouldn't be done here.

   scoped_refptr<device::BluetoothAdvertisement> advertisment_;
   std::unique_ptr<device::BluetoothDiscoverySession> discovery_session_;
   std::unordered_map<std::string,