dbus: fix base class of ErrorResponse

dbus::ErrorResponse needs to be a subclass of dbus::Response otherwise
you can't pass it to a dbus::ExportedObject::ResponseSender.

BUG=none
TEST=my code now compiles

Change-Id: I1efba7c2cd9aaed937cac75133ab6b695aeac63b


Review URL: http://codereview.chromium.org/9675002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@126053 0039d316-1c4b-4281-b951-d872f2087c98

dbus/message.cc

@@ -404,7 +404,7 @@ Response* Response::CreateEmpty() {
 // ErrorResponse implementation.
 //
 
-ErrorResponse::ErrorResponse() : Message() {
+ErrorResponse::ErrorResponse() : Response() {
 }
 
 ErrorResponse* ErrorResponse::FromRawMessage(DBusMessage* raw_message) {

dbus/message.h

@@ -200,16 +200,17 @@ class Response : public Message {
   // 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