Move Extension into extensions namespace

chrome/browser/ui/panels/panel_browser_frame_view.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_PANELS_PANEL_BROWSER_FRAME_VIEW_H_
 #define CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_FRAME_VIEW_H_
 #pragma once
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "chrome/browser/ui/views/frame/browser_non_client_frame_view.h"
 #include "chrome/browser/ui/views/tab_icon_view.h"
 #include "ui/views/controls/button/button.h"
 
-class Extension;
 class PanelBrowserView;
 class SkPaint;
 namespace gfx {
 class Font;
 }
 namespace ui {
 class LinearAnimation;
 }
 namespace views {
 class ImageButton;
@@ skipping 103 matching lines @@
   views::ImageButton* minimize_button_;
   views::ImageButton* restore_button_;
   TabIconView* title_icon_;
   views::Label* title_label_;
   gfx::Rect client_view_bounds_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelBrowserFrameView);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_PANEL_BROWSER_FRAME_VIEW_H_