Simplify adding callbacks.

chrome/browser/ui/webui/chromeos/login/update_screen_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/chromeos/login/update_screen_handler.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/values.h"
 #include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 #include "grit/chromium_strings.h"
@@ skipping 123 matching lines @@
   CallJS("cr.ui.Oobe.showUpdateCurtain", visible_value);
 }
 
 void UpdateScreenHandler::RegisterMessages() {
 #if !defined(OFFICIAL_BUILD)
   AddCallback("cancelUpdate", &UpdateScreenHandler::HandleUpdateCancel);
 #endif
 }
 
 #if !defined(OFFICIAL_BUILD)
-void UpdateScreenHandler::HandleUpdateCancel(const base::ListValue* args) {
-  DCHECK(args && args->empty());
+void UpdateScreenHandler::HandleUpdateCancel() {
   screen_->CancelUpdate();
 }
 #endif
 
 }  // namespace chromeos