This method detects the close button position as configured for the window manager. If you need to know when this key changed, it's best to listen on the schema returned by Granite.Widgets.Utils.get_button_layout_schema for changes and then call this method again.
a Granite.CloseButtonPosition indicating where to best put the close button
if no schema was detected by Granite.Widgets.Utils.get_button_layout_schema or there was no close value in the button-layout string, false will be returned. The position will be LEFT in that case.