chromeos: Convert D-Bus client classes' callback arguments to const reference

chromeos/dbus/mock_cros_disks_client.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 CHROMEOS_DBUS_MOCK_CROS_DISKS_CLIENT_H_
 #define CHROMEOS_DBUS_MOCK_CROS_DISKS_CLIENT_H_
 #pragma once
 
 #include <string>
 
 #include "chromeos/dbus/cros_disks_client.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 namespace chromeos {
 
 class MockCrosDisksClient : public CrosDisksClient {
  public:
   MockCrosDisksClient();
   virtual ~MockCrosDisksClient();
 
-  MOCK_METHOD4(Mount, void(const std::string&, MountType, MountCallback,
-                           ErrorCallback));
-  MOCK_METHOD3(Unmount, void(const std::string&, UnmountCallback,
-                             ErrorCallback));
-  MOCK_METHOD2(EnumerateAutoMountableDevices, void(
-      EnumerateAutoMountableDevicesCallback, ErrorCallback));
-  MOCK_METHOD4(FormatDevice, void(const std::string&, const std::string&,
-                                  FormatDeviceCallback, ErrorCallback));
-  MOCK_METHOD3(GetDeviceProperties, void(
-      const std::string&, GetDevicePropertiesCallback, ErrorCallback));
-  MOCK_METHOD2(SetUpConnections, void(MountEventHandler,
-                                      MountCompletedHandler));
+  MOCK_METHOD4(Mount, void(const std::string&,
+                           MountType,
+                           const MountCallback&,
+                           const ErrorCallback&));
+  MOCK_METHOD3(Unmount, void(const std::string&,
+                             const UnmountCallback&,
+                             const ErrorCallback&));
+  MOCK_METHOD2(EnumerateAutoMountableDevices,
+               void(const EnumerateAutoMountableDevicesCallback&,
+                    const ErrorCallback&));
+  MOCK_METHOD4(FormatDevice, void(const std::string&,
+                                  const std::string&,
+                                  const FormatDeviceCallback&,
+                                  const ErrorCallback&));
+  MOCK_METHOD3(GetDeviceProperties, void(const std::string&,
+                                         const GetDevicePropertiesCallback&,
+                                         const ErrorCallback&));
+  MOCK_METHOD2(SetUpConnections, void(const MountEventHandler&,
+                                      const MountCompletedHandler&));
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_MOCK_CROS_DISKS_CLIENT_H_