chrome: Cleanup class/struct forward declarations

chrome/browser/ui/views/frame/web_contents_close_handler_delegate.h

 // Copyright 2014 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_FRAME_WEB_CONTENTS_CLOSE_HANDLER_DELEGATE_H_
 #define CHROME_BROWSER_UI_VIEWS_FRAME_WEB_CONTENTS_CLOSE_HANDLER_DELEGATE_H_
 
-namespace ui {
-class LayerTreeOwner;
-}
-
 // WebContentsCloseHandler delegate.
 class WebContentsCloseHandlerDelegate {
  public:
   // Invoked to clone the layers of the WebContents. Should do nothing if there
   // is already a clone (eg CloneWebContentsLayer() has been invoked without a
   // DestroyClonedLayer()) or no WebContents. It is expected that when this is
   // invoked the cloned layer tree is drawn on top of the existing WebContents.
   virtual void CloneWebContentsLayer() = 0;
 
   // Invoked to destroy the cloned layer tree. This may be invoked when there is
   // no cloned layer tree.
   virtual void DestroyClonedLayer() = 0;
 
  protected:
   virtual ~WebContentsCloseHandlerDelegate() {}
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_FRAME_WEB_CONTENTS_CLOSE_HANDLER_DELEGATE_H_