Black scrollbar shows up for a a split second before the proper scrollbar

If you have a form with some scrollbars on it, then when starting your application on OS X, your scrollbars will be rendered in dark grey for a split second before being shown 'properly' (i.e. in light grey). I have attached some sample code that illustrates the issue, as well as a screenshot of those dark grey scrollbars and then 'proper' scrollbars.