chrome: Cleanup class/struct forward declarations

chrome/browser/ui/views/dropdown_bar_host.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_DROPDOWN_BAR_HOST_H_
 #define CHROME_BROWSER_UI_VIEWS_DROPDOWN_BAR_HOST_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 #include "ui/gfx/animation/animation_delegate.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/focus/focus_manager.h"
 
 class BrowserView;
 class DropdownBarHostDelegate;
 class DropdownBarView;
 
-namespace content {
-class WebContents;
-}
-
 namespace gfx {
 class SlideAnimation;
 }  // namespace gfx
 
 namespace views {
 class ExternalFocusTracker;
 class View;
 class Widget;
 }  // namespace views
 
@@ skipping 142 matching lines @@
   std::unique_ptr<views::Widget> host_;
 
   // A flag to manually manage visibility. GTK/X11 is asynchronous and
   // the state of the widget can be out of sync.
   bool is_visible_;
 
   DISALLOW_COPY_AND_ASSIGN(DropdownBarHost);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_DROPDOWN_BAR_HOST_H_