Memory management cleanup for the new StyleCachedImage and StyleGeneratedImage classes.  Make the back end
        values hold refptrs to cached front end values.  This will avoid malloc churn as RenderStyles get
        re-resolved.

        Reviewed by olliej

        * css/CSSCursorImageValue.cpp:
        (WebCore::CSSCursorImageValue::updateIfSVGCursorIsUsed):
        (WebCore::CSSCursorImageValue::cachedImage):
        * css/CSSCursorImageValue.h:
        * css/CSSImageGeneratorValue.cpp:
        (WebCore::CSSImageGeneratorValue::CSSImageGeneratorValue):
        (WebCore::CSSImageGeneratorValue::generatedImage):
        * css/CSSImageGeneratorValue.h:
        * css/CSSImageValue.cpp:
        (WebCore::CSSImageValue::CSSImageValue):
        (WebCore::CSSImageValue::~CSSImageValue):
        (WebCore::CSSImageValue::cachedImage):
        * css/CSSImageValue.h:
        * css/CSSStyleSelector.cpp:
        (WebCore::CSSStyleSelector::applyProperty):
        (WebCore::CSSStyleSelector::createStyleImage):
        * css/CSSStyleSelector.h:
        * rendering/RenderStyle.h:
        (WebCore::StyleCachedImage::cachedImage):
        (WebCore::StyleGeneratedImage::StyleGeneratedImage):
        (WebCore::StyleGeneratedImage::data):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@31849 268f45cc-cd09-0410-ab3c-d52691b4dbfc