Use a direct include of strings headers in base/.

base/i18n/rtl.h

 // 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.
 
 #ifndef BASE_I18N_RTL_H_
 #define BASE_I18N_RTL_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/i18n/base_i18n_export.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "build/build_config.h"
 
 namespace base {
 
 class FilePath;
 
 namespace i18n {
 
 const char16 kRightToLeftMark = 0x200F;
 const char16 kLeftToRightMark = 0x200E;
@@ skipping 114 matching lines @@
 // return the text itself. Explicit bidi control characters display and have
 // semantic effect. They can be deleted so they might not always appear in a
 // pair.
 BASE_I18N_EXPORT string16 StripWrappingBidiControlCharacters(
     const string16& text) WARN_UNUSED_RESULT;
 
 }  // namespace i18n
 }  // namespace base
 
 #endif  // BASE_I18N_RTL_H_