RenderEmbeddedObject::isReplacementObscured uses HitTestRequest::IgnoreClipping when hit-testing, causing it to be wrong in light of things like <iframe>. <rdar://problem/14606819>
Actually, we can't not IgnoreClipping, that breaks lots of the other tests. Really what we need to do is climb up the document tree and hit-test from the main document, not from the iframe's document.
The intended behavior gets a bit complicated with scrolling.
Created attachment 209149 [details] patch a little bit concerned about the LayoutRect->IntRect bit.
http://trac.webkit.org/changeset/154412