Remove the ability of webpages to specify strings for the onbeforeunload dialog.

components/app_modal/javascript_dialog_manager.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 COMPONENTS_APP_MODAL_JAVASCRIPT_DIALOG_MANAGER_H_
 #define COMPONENTS_APP_MODAL_JAVASCRIPT_DIALOG_MANAGER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
@@ skipping 34 matching lines @@
   // JavaScriptDialogManager:
   void RunJavaScriptDialog(content::WebContents* web_contents,
                            const GURL& origin_url,
                            const std::string& accept_lang,
                            content::JavaScriptMessageType message_type,
                            const base::string16& message_text,
                            const base::string16& default_prompt_text,
                            const DialogClosedCallback& callback,
                            bool* did_suppress_message) override;
   void RunBeforeUnloadDialog(content::WebContents* web_contents,
-                             const base::string16& message_text,
                              bool is_reload,
                              const DialogClosedCallback& callback) override;
   bool HandleJavaScriptDialog(content::WebContents* web_contents,
                               bool accept,
                               const base::string16* prompt_override) override;
   void CancelActiveAndPendingDialogs(
       content::WebContents* web_contents) override;
   void ResetDialogState(content::WebContents* web_contents) override;
 
   base::string16 GetTitle(content::WebContents* web_contents,
@@ skipping 25 matching lines @@
   // dialogs. (Since Javascript dialogs are modal, this is even accurate!)
   base::TimeTicks last_close_time_;
   base::TimeTicks last_creation_time_;
 
   DISALLOW_COPY_AND_ASSIGN(JavaScriptDialogManager);
 };
 
 }  // namespace app_modal
 
 #endif  // COMPONENTS_APP_MODAL_JAVASCRIPT_DIALOG_MANAGER_H_