Use a direct include of strings headers in chrome/browser/d*/.

chrome/browser/download/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.
 //
 // Download utilities.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if defined(TOOLKIT_VIEWS)
 #include "ui/views/view.h"
 #endif
 
 class GURL;
 
 namespace base {
 class DictionaryValue;
@@ skipping 162 matching lines @@
 
 // Increment one of the above counts.
 void RecordDownloadCount(ChromeDownloadCountTypes type);
 
 // Record initiation of a download from a specific source.
 void RecordDownloadSource(ChromeDownloadSource source);
 
 }  // namespace download_util
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_UTIL_H_