content: Cleanup class/struct forward declarations

content/browser/web_contents/web_contents_view_mac.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 CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_MAC_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "content/browser/renderer_host/render_view_host_delegate_view.h"
 #include "content/browser/web_contents/web_contents_view.h"
 #include "content/common/content_export.h"
 #include "content/common/drag_event_source_info.h"
 #include "ui/base/cocoa/base_view.h"
 #include "ui/gfx/geometry/size.h"
 
 @class FocusTracker;
-class SkBitmap;
 @class WebDragDest;
 @class WebDragSource;
 
 namespace content {
 class PopupMenuHelper;
 class WebContentsImpl;
 class WebContentsViewDelegate;
 class WebContentsViewMac;
 }
 
@@ skipping 116 matching lines @@
   bool allow_other_views_;
 
   std::unique_ptr<PopupMenuHelper> popup_menu_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_MAC_H_