2010-08-05 Tony Chang <tony@chromium.org>

        Reviewed by David Hyatt.

        Fix a crash when a hidden iframe with a custom scrollbar finishes loading an image.
        https://bugs.webkit.org/show_bug.cgi?id=42724

        * scrollbars/hidden-iframe-scrollbar-crash2.html: Added.
        * scrollbars/resources/hidden-iframe-scrollbar-crash2.html: Added.
2010-08-05  Tony Chang  <tony@chromium.org>

        Reviewed by David Hyatt.

        Fix a crash when a hidden iframe with a custom scrollbar finishes loading an image.
        https://bugs.webkit.org/show_bug.cgi?id=42724

        Test: scrollbars/hidden-iframe-scrollbar-crash2.html

        * page/FrameView.cpp:
        (WebCore::FrameView::createScrollbar):
        * rendering/RenderScrollbar.cpp:
        (WebCore::RenderScrollbar::createCustomScrollbar): Pass in Frame
        (WebCore::RenderScrollbar::RenderScrollbar): Pass in Frame
        (WebCore::RenderScrollbar::owningRenderer): Use the frame to get the RenderBox
        (WebCore::RenderScrollbar::getScrollbarPseudoStyle):
        (WebCore::RenderScrollbar::updateScrollbarParts):
        (WebCore::RenderScrollbar::updateScrollbarPart):
        * rendering/RenderScrollbar.h:
        * rendering/RenderScrollbarPart.cpp:
        (WebCore::RenderScrollbarPart::computeScrollbarWidth): null check
        (WebCore::RenderScrollbarPart::computeScrollbarHeight): null check

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@64780 268f45cc-cd09-0410-ab3c-d52691b4dbfc