Make CSS scrollbars respect the OS setting regarding where buttons should be placed.

        Reviewed by Sam Weinig

        No test case possible, since the OS setting can vary.

        * css/CSSSelector.cpp:
        (WebCore::CSSSelector::extractPseudoType):
        * css/CSSSelector.h:
        (WebCore::CSSSelector::):
        * css/CSSStyleSelector.cpp:
        (WebCore::CSSStyleSelector::SelectorChecker::checkScrollbarPseudoClass):
        * platform/Scrollbar.h:
        (WebCore::Scrollbar::styleChanged):
        * platform/mac/ScrollbarThemeMac.mm:
        (+[ScrollbarPrefsObserver appearancePrefsChanged:]):
        (WebCore::ScrollbarThemeMac::preferencesChanged):
        * rendering/RenderLayer.cpp:
        (WebCore::RenderLayer::invalidateScrollbarRect):
        * rendering/RenderScrollbar.cpp:
        (WebCore::RenderScrollbar::styleChanged):
        (WebCore::RenderScrollbar::updateScrollbarPart):
        * rendering/RenderScrollbar.h:
        * rendering/RenderScrollbarTheme.h:
        (WebCore::RenderScrollbarTheme::buttonsPlacement):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@37490 268f45cc-cd09-0410-ab3c-d52691b4dbfc