Comment 11 for bug 422511

I decided to try out my idea from comment #3. This is patch uses a hardcoded value of 2, but that can easily be made configurable, as a murrine specific option. With GtkRange::slider-width set to 18, it gives the same effect for the scrollbars, with none of the bugs.
Yes, it's a hack, but it works, and it's better than using a pixmap engine just for the scrollbars (like Dust does).