Fix "unused variable" warnings.

chrome/browser/extensions/extension_action_icon_factory.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 CHROME_BROWSER_EXTENSIONS_EXTENSION_ACTION_ICON_FACTORY_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_ACTION_ICON_FACTORY_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 37 matching lines @@
   // If there is an icon set using |SetIcon|, that icon is returned.
   // Else, if there is a default icon set for the extension action, the icon is
   // created using IconImage. Observer is triggered wheniever the icon gets
   // updated.
   // Else, extension favicon is returned.
   // In all cases, action's attention and animation icon transformations are
   // applied on the icon.
   gfx::Image GetIcon(int tab_id);
 
  private:
-  const extensions::Extension* extension_;
   const ExtensionAction* action_;
   Observer* observer_;
 
   ScopedObserver<extensions::IconImage, extensions::IconImage::Observer>
       icon_image_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionActionIconFactory);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_ACTION_ICON_FACTORY_H_