chrome: Cleanup class/struct forward declarations

chrome/browser/ui/webui/set_as_default_browser_ui_win.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_WEBUI_SET_AS_DEFAULT_BROWSER_UI_WIN_H_
 #define CHROME_BROWSER_UI_WEBUI_SET_AS_DEFAULT_BROWSER_UI_WIN_H_
 
 #include "base/macros.h"
 #include "ui/web_dialogs/web_dialog_ui.h"
 
-class Browser;
 class Profile;
 
 namespace views {
 class Widget;
 }
 
 // The UI used in first-run flow to prompt the user to set Chrome as the
 // default Windows browser and *the browser* of Metro mode. Intended for
 // Windows 8 only.
 class SetAsDefaultBrowserUI : public ui::WebDialogUI {
  public:
   explicit SetAsDefaultBrowserUI(content::WebUI* web_ui);
 
   // Present metroizer UI either in a new singleton tab or in a dialog window.
   static void Show(Profile* profile);
 
   // Returns the web dialog widget for testing.
   static views::Widget* GetDialogWidgetForTesting();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SetAsDefaultBrowserUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SET_AS_DEFAULT_BROWSER_UI_WIN_H_