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

ui/views/widget/tooltip_manager.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_H_
 #define UI_VIEWS_WIDGET_TOOLTIP_MANAGER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/views_export.h"
 
 namespace gfx {
 class Font;
 }  // namespace gfx
 
 namespace views {
 
 class View;
@@ skipping 40 matching lines @@
                                int* max_width,
                                int* line_count,
                                int x,
                                int y,
                                gfx::NativeView context);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_TOOLTIP_MANAGER_H_