Created an interface for DownloadFile, for use in unit tests.

content/browser/download/drag_download_file.cc

 // Copyright (c) 2011 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/download/drag_download_file.h"
 
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "content/browser/browser_context.h"
 #include "content/browser/download/download_item.h"
 #include "content/browser/download/download_stats.h"
+#include "content/browser/download/download_types.h"
 #include "content/browser/tab_contents/tab_contents.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/file_stream.h"
 
 using content::BrowserThread;
 
 DragDownloadFile::DragDownloadFile(
     const FilePath& file_name_or_path,
     linked_ptr<net::FileStream> file_stream,
     const GURL& url,
@@ skipping 200 matching lines @@
 
 void DragDownloadFile::QuitNestedMessageLoop() {
   AssertCurrentlyOnDragThread();
 
   if (is_running_nested_message_loop_) {
     is_running_nested_message_loop_ = false;
     MessageLoop::current()->Quit();
   }
 }
 #endif