Right now, elementAtPoint will return the inner div. You can see this by trying to use the Web Inspector on the new text field.
These bugs that block us switching to the new text field shoul not be marked P1. Once we turn it on, these would be P1/major bugs, of course, but at the moment they are just part of the "switch to a new text field" task and should not be in the P1 list.
<rdar://problem/4463754> elementAtPoint needs to return input element when clicking on new text field (6813)
Created attachment 7223 [details] patch
Comment on attachment 7223 [details] patch isShadowNode() oughta be const. _actionInformationForNavigationType should probably pass NO for allowShadowContent. Places that check isTextNode and call parentNode might result in nil, and then you are calling shadowAncestorNode without a nil check. Looks great. r=me