add device type as an argument in OnDevicesChanged.

base/test/mock_devices_changed_observer.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 BASE_TEST_MOCK_DEVICES_CHANGED_OBSERVER_H_
 #define BASE_TEST_MOCK_DEVICES_CHANGED_OBSERVER_H_
 
 #include <string>
 
 #include "base/system_monitor/system_monitor.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 namespace base {
 
 class MockDevicesChangedObserver
     : public base::SystemMonitor::DevicesChangedObserver {
  public:
   MockDevicesChangedObserver();
   ~MockDevicesChangedObserver();
 
-  MOCK_METHOD0(OnDevicesChanged, void());
+  MOCK_METHOD1(OnDevicesChanged,
+               void(base::SystemMonitor::DeviceType device_type));
   MOCK_METHOD4(OnMediaDeviceAttached,
                void(const std::string& id,
                     const string16& name,
                     base::SystemMonitor::MediaDeviceType type,
                     const FilePath::StringType& location));
   MOCK_METHOD1(OnMediaDeviceDetached, void(const std::string& id));
 
   DISALLOW_COPY_AND_ASSIGN(MockDevicesChangedObserver);
 };
 
 }  // namespace base
 
 #endif  // BASE_TEST_MOCK_DEVICES_CHANGED_OBSERVER_H_