Add support for list-style-image gradients.  Also improve the image comparisons between two RenderStyles        
        to not mistakenly believe that images have changed.

        Reviewed by olliej

        Added fast/gradients/list-item-gradient.html

        * css/CSSComputedStyleDeclaration.cpp:
        (WebCore::CSSComputedStyleDeclaration::getPropertyCSSValue):
        * css/CSSParser.cpp:
        (WebCore::CSSParser::parseValue):
        * css/CSSStyleSelector.cpp:
        (WebCore::CSSStyleSelector::applyProperty):
        (WebCore::CSSStyleSelector::createStyleImage):
        * rendering/RenderListMarker.cpp:
        (WebCore::RenderListMarker::RenderListMarker):
        (WebCore::RenderListMarker::paint):
        (WebCore::RenderListMarker::imageChanged):
        (WebCore::RenderListMarker::calcPrefWidths):
        * rendering/RenderListMarker.h:
        * rendering/RenderStyle.cpp:
        (WebCore::imagesEquivalent):
        (WebCore::BorderImage::operator==):
        (WebCore::StyleCachedImage::errorOccurred):
        (WebCore::BackgroundLayer::operator==):
        (WebCore::StyleInheritedData::StyleInheritedData):
        (WebCore::cursorDataEquivalent):
        (WebCore::StyleInheritedData::operator==):
        (WebCore::RenderStyle::diff):
        * rendering/RenderStyle.h:
        (WebCore::StyleImage::errorOccurred):
        (WebCore::RenderStyle::listStyleImage):
        (WebCore::RenderStyle::setListStyleImage):
        (WebCore::RenderStyle::initialListStyleImage):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@31845 268f45cc-cd09-0410-ab3c-d52691b4dbfc