Cannot scroll to footer on a page with overflow:hidden on the body
https://bugs.webkit.org/show_bug.cgi?id=114462
-and corresponding-
<rdar://problem/13530042>

Reviewed by Simon Fraser.

Add a new scenario in which we want to overrideHidden -- whenever we are the 
mainFrame and there is a header or footer.

* page/FrameView.cpp:
(WebCore::FrameView::applyOverflowToViewport):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148234 268f45cc-cd09-0410-ab3c-d52691b4dbfc