<https://webkit.org/b/120025> REGRESSION (r154254): fast/frames/frameset-frameborder-inheritance.html failing on Apple MountainLion Debug WK1 (Tests)

Reviewed by Anders Carlsson.

Source/WebCore: 

* html/HTMLDocument.cpp:
(WebCore::HTMLDocument::isFrameSet):
* html/HTMLFrameElement.cpp:
(WebCore::HTMLFrameElement::didAttachRenderers):
        
    Make helper public in HTMLFrameSetElement.

* html/HTMLFrameSetElement.cpp:
(WebCore::HTMLFrameSetElement::findContaining):
        
    Static function for finding containing frameset, if any.

(WebCore::HTMLFrameSetElement::willAttachRenderers):
        
    This broke in refactoring. We should exit the loop when the first containing frameset is found. Fix by refactoring more.

* html/HTMLFrameSetElement.h:
(WebCore::isHTMLFrameSetElement):
(WebCore::toHTMLFrameSetElement):
        
    Add casting functions.

* rendering/RenderFrameSet.cpp:
(WebCore::RenderFrameSet::frameSet):

LayoutTests: 

* platform/mac/TestExpectations: Unskip.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154326 268f45cc-cd09-0410-ab3c-d52691b4dbfc