bluetooth: Forward declare SequencedTaskRunner in BluetoothAdapterChromeOS

device/bluetooth/bluetooth_adapter_chromeos.h

 // Copyright 2013 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_CHROMEOS_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_CHROMEOS_H_
 
 #include <map>
 #include <queue>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
-#include "base/sequenced_task_runner.h"
 #include "chromeos/dbus/bluetooth_adapter_client.h"
 #include "chromeos/dbus/bluetooth_agent_service_provider.h"
 #include "chromeos/dbus/bluetooth_device_client.h"
 #include "chromeos/dbus/bluetooth_input_client.h"
 #include "chromeos/dbus/bluetooth_profile_manager_client.h"
 #include "chromeos/dbus/bluetooth_profile_service_provider.h"
 #include "dbus/object_path.h"
 #include "device/bluetooth/bluetooth_adapter.h"
 #include "device/bluetooth/bluetooth_audio_sink.h"
 #include "device/bluetooth/bluetooth_device.h"
 #include "device/bluetooth/bluetooth_discovery_session.h"
 #include "device/bluetooth/bluetooth_export.h"
 
+namespace base {
+class SequencedTaskRunner;
+}  // namespace base
+
 namespace device {
 class BluetoothSocketThread;
 }  // namespace device
 
 namespace chromeos {
 
 class BluetoothChromeOSTest;
 class BluetoothAdapterProfileChromeOS;
 class BluetoothDeviceChromeOS;
 class BluetoothPairingChromeOS;
@@ skipping 335 matching lines @@
   // 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<BluetoothAdapterChromeOS> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BluetoothAdapterChromeOS);
 };
 
 }  // namespace chromeos
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_CHROMEOS_H_