dbus: Add ObjectProxy::EmptyResponseCallback().

dbus/object_proxy.h

 // Copyright (c) 2011 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 DBUS_OBJECT_PROXY_H_
 #define DBUS_OBJECT_PROXY_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 55 matching lines @@
   //
   // BLOCKING CALL.
   virtual Response* CallMethodAndBlock(MethodCall* method_call,
                                        int timeout_ms);
 
   // Requests to call the method of the remote object.
   //
   // |callback| will be called in the origin thread, once the method call
   // is complete. As it's called in the origin thread, |callback| can
   // safely reference objects in the origin thread (i.e. UI thread in most
-  // cases).
+  // cases). If the caller is not interested in the response from the
+  // method (i.e. calling a method that does not return a value),
+  // EmptyResponseCallback() can be passed to the |callback| parameter.
   //
   // If the method call is successful, a pointer to Response object will
   // be passed to the callback. If unsuccessful, NULL will be passed to
   // the callback.
   //
   // Must be called in the origin thread.
   virtual void CallMethod(MethodCall* method_call,
                           int timeout_ms,
                           ResponseCallback callback);
 
@@ skipping 12 matching lines @@
                                const std::string& signal_name,
                                SignalCallback signal_callback,
                                OnConnectedCallback on_connected_callback);
 
   // Detaches from the remote object. The Bus object will take care of
   // detaching so you don't have to do this manually.
   //
   // BLOCKING CALL.
   virtual void Detach();
 
+  // Returns an empty callback that does nothing. Can be used for
+  // CallMethod().
+  static ResponseCallback EmptyResponseCallback();
+
  protected:
   // This is protected, so we can define sub classes.
   virtual ~ObjectProxy();
 
  private:
   friend class base::RefCountedThreadSafe<ObjectProxy>;
 
   // Struct of data we'll be passing from StartAsyncMethodCall() to
   // OnPendingCallIsCompleteThunk().
   struct OnPendingCallIsCompleteData {
@@ skipping 69 matching lines @@
   MethodTable method_table_;
 
   std::vector<std::string> match_rules_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectProxy);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_OBJECT_PROXY_H_