To reproduce: 1. Go to http://milliondollarcu.be/ 2. Spoof as Safari Mac (otherwise the site won't kick into 3D mode) 3. Resize the window so there's a horizontal scrollbar The page's content draws over the horizontal scrollbar. See screenshot.
Created attachment 46918 [details] screenshot
<rdar://problem/7556105>
Created attachment 47367 [details] Patch
Landed in http://trac.webkit.org/changeset/53814