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

device/bluetooth/bluetooth_adapter.cc

 // 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.
 
 #include "device/bluetooth/bluetooth_adapter.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 37 matching lines @@
 void BluetoothAdapter::AddObserver(BluetoothAdapter::Observer* observer) {
   DCHECK(observer);
   observers_.AddObserver(observer);
 }
 
 void BluetoothAdapter::RemoveObserver(BluetoothAdapter::Observer* observer) {
   DCHECK(observer);
   observers_.RemoveObserver(observer);
 }
 
+bool BluetoothAdapter::HasObserver(BluetoothAdapter::Observer* observer) {
+  return observers_.HasObserver(observer);

[rkc, 2016/08/08 23:53:33]

Before this line,
DCHECK(observer);

[puthik_chromium, 2016/08/09 00:08:57]

Added.
Actually, It would just return false if observer is null anyway.

+}
+
 void BluetoothAdapter::StartDiscoverySession(
     const DiscoverySessionCallback& callback,
     const ErrorCallback& error_callback) {
   StartDiscoverySessionWithFilter(nullptr, callback, error_callback);
 }
 
 void BluetoothAdapter::StartDiscoverySessionWithFilter(
     std::unique_ptr<BluetoothDiscoveryFilter> discovery_filter,
     const DiscoverySessionCallback& callback,
     const ErrorCallback& error_callback) {
@@ skipping 343 matching lines @@
   UMA_HISTOGRAM_ENUMERATION(
       "Bluetooth.DiscoverySession.Stop.Outcome", static_cast<int>(outcome),
       static_cast<int>(UMABluetoothDiscoverySessionOutcome::COUNT));
 }
 
 // static
 const base::TimeDelta BluetoothAdapter::timeoutSec =
     base::TimeDelta::FromSeconds(180);
 
 }  // namespace device