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

ui/message_center/notifier_settings.h

 // Copyright (c) 2013 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_NOTIFIER_SETTINGS_H_
 #define UI_MESSAGE_CENTER_NOTIFIER_SETTINGS_H_
 
 #include <string>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "googleurl/src/gurl.h"
 #include "ui/gfx/image/image.h"
 #include "ui/message_center/message_center_export.h"
 
 namespace message_center {
 
 class NotifierSettingsDelegate;
 class NotifierSettingsProvider;
 
 // Brings up the settings dialog and returns a weak reference to the delegate,
@@ skipping 84 matching lines @@
   virtual void UpdateIconImage(const std::string& id,
                                const gfx::Image& icon) = 0;
 
   // Called when the controller detects that a favicon has changed.
   virtual void UpdateFavicon(const GURL& url, const gfx::Image& icon) = 0;
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_NOTIFIER_SETTINGS_H_