Start splitting out WebUI into an implementation class and an interface that each page implements...

chrome/browser/ui/webui/extensions/extensions_ui.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_WEBUI_EXTENSIONS_EXTENSIONS_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSIONS_UI_H_
 #pragma once
 
 #include "content/browser/webui/web_ui.h"
+#include "content/public/browser/web_ui_controller.h"
 
-class ExtensionsUI : public WebUI {
+class ExtensionsUI : public WebUI, public content::WebUIController {
  public:
   explicit ExtensionsUI(content::WebContents* contents);
   virtual ~ExtensionsUI();
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSIONS_UI_H_