chrome: Cleanup class/struct forward declarations

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"
 #include "base/scoped_observer.h"
 #include "extensions/browser/extension_icon_image.h"
 
 class ExtensionAction;
-class ExtensionIconSet;
 class Profile;
 
 namespace extensions {
 class Extension;
 }
 
 // Used to get an icon to be used in the UI for an extension action.
 // If the extension action icon is the default icon defined in the extension's
 // manifest, it is loaded using extensions::IconImage. This icon can be loaded
 // asynchronously. The factory observes underlying IconImage and notifies its
@@ skipping 32 matching lines @@
   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_