Use a direct include of strings headers in base/.

base/i18n/time_formatting.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.
 
 // Basic time formatting methods.  These methods use the current locale
 // formatting for displaying the time.
 
 #ifndef BASE_I18N_TIME_FORMATTING_H_
 #define BASE_I18N_TIME_FORMATTING_H_
 
 #include "base/i18n/base_i18n_export.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 namespace base {
 
 class Time;
 
 // Argument type used to specify the hour clock type.
 enum HourClockType {
   k12HourClock,  // Uses 1-12. e.g., "3:07 PM"
   k24HourClock,  // Uses 0-23. e.g., "15:07"
 };
@@ skipping 34 matching lines @@
 BASE_I18N_EXPORT string16 TimeFormatFriendlyDate(const Time& time);
 
 // Gets the hour clock type of the current locale. e.g.
 // k12HourClock (en-US).
 // k24HourClock (en-GB).
 BASE_I18N_EXPORT HourClockType GetHourClockType();
 
 }  // namespace base
 
 #endif  // BASE_I18N_TIME_FORMATTING_H_