dbus: fix base class of ErrorResponse

dbus/message.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_MESSAGE_H_
 #define DBUS_MESSAGE_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 182 matching lines @@
 
   // Returns a newly created Response from the given method call. The
   // caller must delete the returned object. Used for implementing
   // exported methods.
   static Response* FromMethodCall(MethodCall* method_call);
 
   // Returns a newly created Response with an empty payload. The caller
   // must delete the returned object. Useful for testing.
   static Response* CreateEmpty();
 
- private:
+ protected:
   // Creates a Response message. The internal raw message is NULL.
   Response();
 
+ private:
   DISALLOW_COPY_AND_ASSIGN(Response);
 };
 
 // ErrorResponse is a type of message used to return an error to the
 // caller of a method.
-class ErrorResponse: public Message {
+class ErrorResponse: public Response {
  public:
   // Returns a newly created Response from the given raw message of the
   // type DBUS_MESSAGE_TYPE_METHOD_RETURN. The caller must delete the
   // returned object. Takes the ownership of |raw_message|.
   static ErrorResponse* FromRawMessage(DBusMessage* raw_message);
 
   // Returns a newly created ErrorResponse from the given method call, the
   // error name, and the error message.  The error name looks like
   // "org.freedesktop.DBus.Error.Failed". Used for returning an error to a
   // failed method call.
@@ skipping 237 matching lines @@
 
   Message* message_;
   DBusMessageIter raw_message_iter_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageReader);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_MESSAGE_H_