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

content/browser/frame_host/render_frame_host_delegate.h

 // Copyright 2013 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 CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_DELEGATE_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 63 matching lines @@
 
   // A JavaScript message, confirmation or prompt should be shown.
   virtual void RunJavaScriptMessage(RenderFrameHost* render_frame_host,
                                     const base::string16& message,
                                     const base::string16& default_prompt,
                                     const GURL& frame_url,
                                     JavaScriptMessageType type,
                                     IPC::Message* reply_msg) {}
 
   virtual void RunBeforeUnloadConfirm(RenderFrameHost* render_frame_host,
-                                      const base::string16& message,
                                       bool is_reload,
                                       IPC::Message* reply_msg) {}
 
   // Another page accessed the top-level initial empty document, which means it
   // is no longer safe to display a pending URL without risking a URL spoof.
   virtual void DidAccessInitialDocument() {}
 
   // The frame changed its window.name property.
   virtual void DidChangeName(RenderFrameHost* render_frame_host,
                              const std::string& name) {}
@@ skipping 97 matching lines @@
   virtual gfx::NativeViewAccessible GetParentNativeViewAccessible();
 #endif
 
  protected:
   virtual ~RenderFrameHostDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_DELEGATE_H_