Move string files in base/ to the string subdirectory.

base/strings/string_util_posix.h

Index: base/strings/string_util_posix.h
diff --git a/base/string_util_posix.h b/base/strings/string_util_posix.h
similarity index 88%
copy from base/string_util_posix.h
copy to base/strings/string_util_posix.h
index 9b776e66aa526fb0bc1bcb0dca437c182a1d52b6..382637c61958cff8693999ab3475d10ddd236b8d 100644
--- a/base/string_util_posix.h
+++ b/base/strings/string_util_posix.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef BASE_STRING_UTIL_POSIX_H_
-#define BASE_STRING_UTIL_POSIX_H_
+#ifndef BASE_STRINGS_STRING_UTIL_POSIX_H_
+#define BASE_STRINGS_STRING_UTIL_POSIX_H_
 
 #include <stdarg.h>
 #include <stdio.h>
@@ -11,7 +11,7 @@
 #include <wchar.h>
 
 #include "base/logging.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 
 namespace base {
 
@@ -50,4 +50,4 @@ inline int vswprintf(wchar_t* buffer, size_t size,
 
 }  // namespace base
 
-#endif  // BASE_STRING_UTIL_POSIX_H_
+#endif  // BASE_STRINGS_STRING_UTIL_POSIX_H_