Use a direct include of strings headers in ui/, part 2.

ui/message_center/notification_list.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 UI_MESSAGE_CENTER_NOTIFICATION_LIST_H_
 #define UI_MESSAGE_CENTER_NOTIFICATION_LIST_H_
 
 #include <set>
 #include <string>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/time.h"
 #include "base/timer.h"
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/message_center/message_center_export.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_types.h"
 
 namespace base {
 class DictionaryValue;
@@ skipping 125 matching lines @@
   size_t unread_count_;
   bool quiet_mode_;
   scoped_ptr<base::OneShotTimer<NotificationList> > quiet_mode_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationList);
 };
 
 }  // namespace message_center
 
 #endif // UI_MESSAGE_CENTER_NOTIFICATION_LIST_H_