Move string files in base/ to the string subdirectory.

base/strings/string_util_win.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 BASE_STRING_UTIL_WIN_H_
-#define BASE_STRING_UTIL_WIN_H_
+#ifndef BASE_STRINGS_STRING_UTIL_WIN_H_
+#define BASE_STRINGS_STRING_UTIL_WIN_H_
 
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #include <wchar.h>
 
 #include "base/logging.h"
 
 namespace base {
 
@@ skipping 34 matching lines @@
   if (length < 0) {
     if (size > 0)
       buffer[0] = 0;
     return _vscwprintf_p(format, arguments);
   }
   return length;
 }
 
 }  // namespace base
 
-#endif  // BASE_STRING_UTIL_WIN_H_
+#endif  // BASE_STRINGS_STRING_UTIL_WIN_H_