Some green boxes that should be visible in fast/layers/layer-visibility.html and fast/layers/layer-visibility-sublayer.html are invisible following <http://trac.webkit.org/projects/webkit/changeset/23773> (fix for bug 14297).
It was Antti who tracked it down to r23773!
<rdar://problem/5346697> Fixed by Antti in <http://trac.webkit.org/projects/webkit/changeset/24447>.