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

chromeos/dbus/flimflam_client_unittest_base.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_FLIMFLAM_CLIENT_UNITTEST_BASE_H_
 #define CHROMEOS_DBUS_FLIMFLAM_CLIENT_UNITTEST_BASE_H_
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
@@ skipping 29 matching lines @@
   virtual void SetUp() OVERRIDE;
   virtual void TearDown() OVERRIDE;
 
  protected:
   // A callback to intercept and check the method call arguments.
   typedef base::Callback<void(
       dbus::MessageReader* reader)> ArgumentCheckCallback;
 
   // Sets expectations for called method name and arguments, and sets response.
   void PrepareForMethodCall(const std::string& method_name,
-                            ArgumentCheckCallback argument_checker,
+                            const ArgumentCheckCallback& argument_checker,
                             dbus::Response* response);
 
   // Sends property changed signal to the tested client.
   void SendPropertyChangedSignal(dbus::Signal* signal);
 
   // Checks the name and the value which are sent by PropertyChanged signal.
   static void ExpectPropertyChanged(const std::string& expected_name,
                                     const base::Value* expected_value,
                                     const std::string& name,
                                     const base::Value& value);
@@ skipping 27 matching lines @@
   MessageLoop message_loop_;
   // The mock bus.
   scoped_refptr<dbus::MockBus> mock_bus_;
 
  private:
   // Checks the requested interface name and signal name.
   // Used to implement the mock proxy.
   void OnConnectToSignal(
       const std::string& interface_name,
       const std::string& signal_name,
-      dbus::ObjectProxy::SignalCallback signal_callback,
-      dbus::ObjectProxy::OnConnectedCallback on_connected_callback);
+      const dbus::ObjectProxy::SignalCallback& signal_callback,
+      const dbus::ObjectProxy::OnConnectedCallback& on_connected_callback);
 
   // Checks the content of the method call and returns the response.
   // Used to implement the mock proxy.
-  void OnCallMethod(dbus::MethodCall* method_call,
-                    int timeout_ms,
-                    dbus::ObjectProxy::ResponseCallback response_callback);
+  void OnCallMethod(
+      dbus::MethodCall* method_call,
+      int timeout_ms,
+      const dbus::ObjectProxy::ResponseCallback& response_callback);
 
   // The interface name.
   const std::string interface_name_;
   // The mock object proxy.
   scoped_refptr<dbus::MockObjectProxy> mock_proxy_;
   // The PropertyChanged signal handler given by the tested client.
   dbus::ObjectProxy::SignalCallback property_changed_handler_;
   // The name of the method which is expected to be called.
   std::string expected_method_name_;
   // The response which the mock object proxy returns.
   dbus::Response* response_;
   // A callback to intercept and check the method call arguments.
   ArgumentCheckCallback argument_checker_;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_FLIMFLAM_CLIENT_UNITTEST_BASE_H_