Clean up RenderFrameSet::nodeAtPoint
https://bugs.webkit.org/show_bug.cgi?id=112450

Reviewed by Eric Seidel.

Remove handling of resizing framesets from RenderFrameSet::nodeAtPoint.
The code has been incorrect since a mistake in r18333 (December 2006),
but has been dead code since r17770 (November 2006) where the then new
EventHandler started taking care of routing events to resizing FrameSets.

Since this was the only special feature of RenderFrameSet::nodeAtPoint,
the method has been removed.

* rendering/RenderFrameSet.cpp:
* rendering/RenderFrameSet.h:
(RenderFrameSet):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146056 268f45cc-cd09-0410-ab3c-d52691b4dbfc