Use a direct include of strings headers in ui/, part 3.

ui/views/widget/tooltip_manager_win.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 UI_VIEWS_WIDGET_TOOLTIP_MANAGER_WIN_H_
 #define UI_VIEWS_WIDGET_TOOLTIP_MANAGER_WIN_H_
 
 #include <windows.h>
 #include <commctrl.h>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/point.h"
 #include "ui/views/widget/tooltip_manager.h"
 
 namespace gfx {
 class Point;
 }
 
 namespace views {
 
@@ skipping 118 matching lines @@
   // Used to register DestroyTooltipWindow function with PostDelayedTask
   // function.
   base::WeakPtrFactory<TooltipManagerWin> keyboard_tooltip_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TooltipManagerWin);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_TOOLTIP_MANAGER_WIN_H_