chrome: Cleanup class/struct forward declarations

chrome/browser/ui/views/download/download_shelf_context_menu_view.h

 // Copyright (c) 2011 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_DOWNLOAD_DOWNLOAD_SHELF_CONTEXT_MENU_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_DOWNLOAD_DOWNLOAD_SHELF_CONTEXT_MENU_VIEW_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "chrome/browser/download/download_shelf_context_menu.h"
 #include "chrome/browser/ui/views/download/download_item_view.h"
 #include "ui/base/ui_base_types.h"
 
-namespace content {
-class DownloadItem;
-class PageNavigator;
-}
-
 namespace gfx {
 class Rect;
 }
 
 namespace views {
 class MenuRunner;
 class Widget;
 }
 
 class DownloadShelfContextMenuView : public DownloadShelfContextMenu {
@@ skipping 21 matching lines @@
 
   std::unique_ptr<views::MenuRunner> menu_runner_;
 
   // Time the menu was closed.
   base::TimeTicks close_time_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadShelfContextMenuView);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_DOWNLOAD_DOWNLOAD_SHELF_CONTEXT_MENU_VIEW_H_