When an element is in the middle of an accelerated animation/transition, we need to ensure that hit-testing on that element works by computing where the element is in the transition (since hardware transitions don't do layout on every step).
<rdar://problem/6366064>
Created attachment 27676 [details] Patch with tests
Comment on attachment 27676 [details] Patch with tests r=me
http://trac.webkit.org/changeset/41214