content: Cleanup class/struct forward declarations

content/browser/download/drag_download_file.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_DOWNLOAD_DRAG_DOWNLOAD_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DRAG_DOWNLOAD_FILE_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "content/browser/download/download_file.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/common/referrer.h"
 #include "ui/base/dragdrop/download_file_interface.h"
 #include "url/gurl.h"
 
 namespace content {
 
-class DownloadManager;
 class WebContents;
 
 // This class implements downloading a file via dragging virtual files out of
 // the browser:
 // http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-August/022118.html
 // http://www.html5rocks.com/en/tutorials/casestudies/box_dnd_download/
 class CONTENT_EXPORT DragDownloadFile : public ui::DownloadFileProvider {
  public:
   // On Windows, we need to download into a temporary file. On posix, we need to
   // download into a file that has already been created, so only the UI
@@ skipping 28 matching lines @@
   base::RunLoop nested_loop_;
   DragDownloadFileUI* drag_ui_;
   base::WeakPtrFactory<DragDownloadFile> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DragDownloadFile);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DRAG_DOWNLOAD_FILE_H_