Comment 2 for bug 1523898

That should be possible, although not quite sure which file needs to be customized.

Reading through https://css-tricks.com/custom-scrollbars-in-webkit/, it looks like the UITK style can be mimicked with CSS only. We should keep in mind that oxide is toolkit-agnostic though, so we might want to make the scrollbar style customizable by embedders, rather than hardcoding a specific style for everyone.