Reviewed by Chris.

    Reviewed by Chris.

        Fix for <rdar://problem/4023393> Safari crashed in khtml::RenderObject::repaintAfterLayoutIfNeeded(QRect const&, QRect const&)

        We were crashing after hitting PageDown when viewing a pdf because
        WebKit was calling over to WebCore to scroll overflow areas.
        Since this only needs to be done if we're dealing with a WebHTMLView,
        I added a wrapper function to check the documentView before calling
        over to WebCore.

        * WebView.subproj/WebFrameView.m:
        (-[WebFrameView _scrollOverflowInDirection:granularity:]): added wrapper function that checks if documentView is a WebHTMLView
        (-[WebFrameView scrollToBeginningOfDocument:]): uses new wrapper function now
        (-[WebFrameView scrollToEndOfDocument:]): uses new wrapper function now
        (-[WebFrameView _pageVertically:]): uses new wrapper function now
        (-[WebFrameView _pageHorizontally:]): uses new wrapper function now
        (-[WebFrameView _scrollLineVertically:]): uses new wrapper function now
        (-[WebFrameView _scrollLineHorizontally:]): uses new wrapper function now

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8688 268f45cc-cd09-0410-ab3c-d52691b4dbfc