Reviewed by Brady.

        http://bugzilla.opendarwin.org/show_bug.cgi?id=9777
        Reproducible crash in Loading/Frames in ToT.
        
        The problem was that the renderpart destructor resets the frame's 
        owner element. For iframes, this should only be done when the element is 
        going to be removed from the document.
        
        * html/HTMLIFrameElement.cpp:
        (WebCore::HTMLIFrameElement::~HTMLIFrameElement):
        (WebCore::HTMLIFrameElement::willRemove):
        (WebCore::HTMLIFrameElement::removedFromDocument):
        (WebCore::HTMLIFrameElement::detach):        
        * html/HTMLIFrameElement.h:
        Remove the frame in willRemove instead.
        
        * rendering/RenderPart.cpp:
        (WebCore::RenderPart::RenderPart):
        (WebCore::RenderPart::~RenderPart):
        * rendering/RenderPart.h:
        Don't call setFrame(0) in the destructor when the element is an iframe element.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15219 268f45cc-cd09-0410-ab3c-d52691b4dbfc