Reland add --use-more-webui runtime flag to toggle WebUI replacements for native dialogs.

chrome/browser/ui/browser_dialogs.h

 // Copyright (c) 2011 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 CHROME_BROWSER_UI_BROWSER_DIALOGS_H_
 #define CHROME_BROWSER_UI_BROWSER_DIALOGS_H_
 #pragma once
 
 #include "ipc/ipc_message.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 33 matching lines @@
                                   Browser* browser,
                                   const SkBitmap& icon,
                                   Profile* profile);
 
 // Shows or hide the hung renderer dialog for the given TabContents.
 // We need to pass the TabContents to the dialog, because multiple tabs can hang
 // and it needs to keep track of which tabs are currently hung.
 void ShowHungRendererDialog(TabContents* contents);
 void HideHungRendererDialog(TabContents* contents);
 
+// Native implementations of hung renderer dialogs.
+void ShowNativeHungRendererDialog(TabContents* contents);
+void HideNativeHungRendererDialog(TabContents* contents);
+
 } // namespace browser
 
 #endif  // CHROME_BROWSER_UI_BROWSER_DIALOGS_H_