The various methods that map rects and quads between absolute and local coords needs to map through 3d transforms just like localToAbsolute()/absoluteToLocal().
Created attachment 28384 [details] Patch, changelog
I think the TransformState in this patch could also be used as-is for hit testing now, eliminating the need for HitTestingTransformState.
This patch also fixes bug 23283.
Comment on attachment 28384 [details] Patch, changelog r=me
http://trac.webkit.org/changeset/41531