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

device/bluetooth/bluetooth_adapter.h

 // Copyright (c) 2012 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_ADAPTER_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 249 matching lines @@
   // no Bluetooth controller exists in the local system. |IsPresent| will return
   // false.
   virtual void Shutdown();
 #endif
 
   // Adds and removes observers for events on this bluetooth adapter. If
   // monitoring multiple adapters, check the |adapter| parameter of observer
   // methods to determine which adapter is issuing the event.
   virtual void AddObserver(BluetoothAdapter::Observer* observer);
   virtual void RemoveObserver(BluetoothAdapter::Observer* observer);
+  virtual bool HasObserver(BluetoothAdapter::Observer* observer);
 
   // The address of this adapter. The address format is "XX:XX:XX:XX:XX:XX",
   // where each XX is a hexadecimal number.
   virtual std::string GetAddress() const = 0;
 
   // The name of the adapter.
   virtual std::string GetName() const = 0;
 
   // Set the human-readable name of the adapter to |name|. On success,
   // |callback| will be called. On failure, |error_callback| will be called.
@@ skipping 327 matching lines @@
   std::set<BluetoothDiscoverySession*> discovery_sessions_;
 
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<BluetoothAdapter> weak_ptr_factory_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_H_