Use a direct include of strings headers in content/browser/, part 1.

content/browser/download/drag_download_util.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_UTIL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DRAG_DOWNLOAD_UTIL_H_
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "content/browser/download/drag_download_file.h"
 #include "ui/base/dragdrop/download_file_interface.h"
 
 class GURL;
 
 namespace base {
 class FilePath;
 }
 
 namespace net {
@@ skipping 39 matching lines @@
   void Cleanup();
 
   scoped_refptr<DragDownloadFile> drag_file_downloader_;
 
   DISALLOW_COPY_AND_ASSIGN(PromiseFileFinalizer);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DRAG_DOWNLOAD_UTIL_H_