chrome: Cleanup class/struct forward declarations

chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item_tab.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_ASH_LAUNCHER_CHROME_LAUNCHER_APP_MENU_ITEM_TAB_H_
 #define CHROME_BROWSER_UI_ASH_LAUNCHER_CHROME_LAUNCHER_APP_MENU_ITEM_TAB_H_
 
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "chrome/browser/ui/ash/launcher/chrome_launcher_app_menu_item.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace content{
 class WebContents;
 }
 
-class TabStripModel;
-
 // A menu item controller for a running browser tab. It gets created when an
 // application/tab list gets created. It's main purpose is to add the
 // activation method to the |ChromeLauncherAppMenuItem| class.
 class ChromeLauncherAppMenuItemTab
     : public ChromeLauncherAppMenuItem,
       public content::WebContentsObserver {
  public:
   ChromeLauncherAppMenuItemTab(const base::string16 title,
                                const gfx::Image* icon,
                                content::WebContents* content,
                                bool has_leading_separator);
   bool IsActive() const override;
   bool IsEnabled() const override;
   void Execute(int event_flags) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ChromeLauncherAppMenuItemTab);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_LAUNCHER_CHROME_LAUNCHER_APP_MENU_ITEM_TAB_H_