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

content/browser/web_contents/web_contents_drag_win.cc

 // 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.
 
 #include "content/browser/web_contents/web_contents_drag_win.h"
 
 #include <windows.h>
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/message_loop.h"
 #include "base/pickle.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread.h"
 #include "base/utf_string_conversions.h"
 #include "content/browser/download/drag_download_file.h"
 #include "content/browser/download/drag_download_util.h"
 #include "content/browser/web_contents/web_drag_dest_win.h"
 #include "content/browser/web_contents/web_drag_source_win.h"
 #include "content/browser/web_contents/web_drag_utils_win.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_drag_dest_delegate.h"
 #include "net/base/net_util.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/clipboard/clipboard_util_win.h"
 #include "ui/base/clipboard/custom_data_helper.h"
 #include "ui/base/dragdrop/drag_utils.h"
 #include "ui/base/layout.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/screen.h"
 #include "ui/gfx/size.h"
 #include "webkit/glue/webdropdata.h"
 
 using content::BrowserThread;
@@ skipping 330 matching lines @@
 void WebContentsDragWin::OnDataObjectDisposed() {
   DCHECK(drag_drop_thread_id_ == base::PlatformThread::CurrentId());
 
   // The drag-and-drop thread is only closed after OLE is done with
   // DataObjectImpl.
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(&WebContentsDragWin::CloseThread, this));
 }