Use a direct include of strings headers in chrome/browser/r*-s*/.

chrome/browser/status_icons/desktop_notification_balloon.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 CHROME_BROWSER_STATUS_ICONS_DESKTOP_NOTIFICATION_BALLOON_H_
 #define CHROME_BROWSER_STATUS_ICONS_DESKTOP_NOTIFICATION_BALLOON_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 class Notification;
 
 namespace gfx {
 class ImageSkia;
 }
 
 // Provides the notification balloon functionality by using desktop
 // notifications to platforms that don't have a specific native API.
 class DesktopNotificationBalloon {
  public:
   DesktopNotificationBalloon();
   virtual ~DesktopNotificationBalloon();
 
   void DisplayBalloon(const gfx::ImageSkia& icon,
                       const string16& title,
                       const string16& contents);
 
  private:
   std::string notification_id_;
 
   // Counter to provide unique ids to notifications.
   static int id_count_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopNotificationBalloon);
 };
 
 #endif  // CHROME_BROWSER_STATUS_ICONS_DESKTOP_NOTIFICATION_BALLOON_H_