Move Extension into extensions namespace

chrome/browser/ui/views/ash/extension_utils.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_UI_VIEWS_ASH_EXTENSION_UTILS_H_
 #define CHROME_BROWSER_UI_VIEWS_ASH_EXTENSION_UTILS_H_
 #pragma once
 
 class Profile;
+
+namespace extensions {
 class Extension;
+}
 
 namespace extension_utils {
 
 // Opens an extension.  |event_flags| holds the flags of the event
 // which triggered this extension.
 void OpenExtension(Profile* profile,
-                   const Extension* extension,
+                   const extensions::Extension* extension,
                    int event_flags);
 
 }  // namespace extension_utils
 
 #endif  // CHROME_BROWSER_UI_VIEWS_ASH_EXTENSION_UTILS_H_