dbus: Rewrite ObjectProxy::CallMethodWithErrorCallback's comment

dbus/object_proxy.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 DBUS_OBJECT_PROXY_H_
 #define DBUS_OBJECT_PROXY_H_
 
 #include <dbus/dbus.h>
 
 #include <map>
@@ skipping 119 matching lines @@
 
   // Requests to call the method of the remote object.
   //
   // |callback| and |error_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). 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, the error callback will be
-  // called and a pointer to ErrorResponse object will be passed to the error
-  // callback if available, otherwise NULL will be passed.
+  // If the method call is successful, |callback| will be invoked with a
+  // Response object. If unsuccessful, |error_callback| will be invoked with an
+  // ErrorResponse object (if the remote object returned an error) or nullptr
+  // (if a response was not received at all).
   //
   // Must be called in the origin thread.
   virtual void CallMethodWithErrorCallback(MethodCall* method_call,
                                            int timeout_ms,
                                            ResponseCallback callback,
                                            ErrorCallback error_callback);
 
   // Requests to connect to the signal from the remote object.
   //
   // |signal_callback| will be called in the origin thread, when the
@@ skipping 174 matching lines @@
   std::string service_name_owner_;
 
   std::set<DBusPendingCall*> pending_calls_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectProxy);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_OBJECT_PROXY_H_