Reviewed by Benjamin Poulain.

        [Qt] Mask the QStyle::State_Horizontal hint for vertical scrollbars.

        When initializing a QStyleOptionSlider from a widget, the State_Horizontal
        hint may get set depending on how that widget is laid out in its parent.
        If this happens when drawing a vertical scrollbar, the hint is never
        cleared and we end up painting a vertical scrollbar with horizontal arrows.

        Covered by pixel tests which should no longer paint silly scrollbars.

        * platform/qt/ScrollbarThemeQt.cpp:
        (WebCore::styleOptionSlider):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@83160 268f45cc-cd09-0410-ab3c-d52691b4dbfc