content: Forward declare SkBitmap instead of including its header file.

content/browser/web_contents/web_contents_drag_win.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_DRAG_WIN_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_DRAG_WIN_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/platform_thread.h"
 #include "content/common/content_export.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebDragOperation.h"
-#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/dragdrop/os_exchange_data_provider_win.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/point.h"
 
 class DragDropThread;
+class SkBitmap;
 class WebDragDest;
 class WebDragSource;
 struct WebDropData;
 
 namespace content {
 class WebContents;
 }
 
 namespace gfx {
 class ImageSkia;
@@ skipping 74 matching lines @@
 
   // The flag to guard that EndDragging is not called twice.
   bool drag_ended_;
 
   base::Callback<void()> drag_end_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsDragWin);
 };
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_DRAG_WIN_H_