Reviewed by Eric Seidel.

        Refcount Images used in rendering code
        https://bugs.webkit.org/show_bug.cgi?id=52701

        Change StyleImage::image(RenderObject*, const IntSize&) and
        CSSImageGeneratorValue::image(RenderObject*, const IntSize&) to
        return PassRefPtr<Image>, and adjust other code accordingly.

        This allows us to return one-time images, for example for CSS gradients
        whose appearance may change depending on factors other than the renderer
        and the destination size.

        * css/CSSCanvasValue.cpp:
        (WebCore::CSSCanvasValue::image):
        * css/CSSCanvasValue.h:
        * css/CSSGradientValue.cpp:
        (WebCore::CSSGradientValue::image):
        * css/CSSGradientValue.h:
        * css/CSSImageGeneratorValue.h:
        * rendering/RenderBoxModelObject.cpp:
        (WebCore::RenderBoxModelObject::paintFillLayerExtended):
        (WebCore::RenderBoxModelObject::paintNinePieceImage):
        * rendering/RenderImage.cpp:
        (WebCore::RenderImage::paintReplaced):
        (WebCore::RenderImage::paintIntoRect):
        * rendering/RenderImageResource.h:
        (WebCore::RenderImageResource::image):
        * rendering/RenderImageResourceStyleImage.h:
        (WebCore::RenderImageResourceStyleImage::image):
        * rendering/RenderListMarker.cpp:
        (WebCore::RenderListMarker::paint):
        * rendering/style/StyleCachedImage.cpp:
        (WebCore::StyleCachedImage::image):
        * rendering/style/StyleCachedImage.h:
        * rendering/style/StyleGeneratedImage.cpp:
        (WebCore::StyleGeneratedImage::image):
        * rendering/style/StyleGeneratedImage.h:
        * rendering/style/StyleImage.h:
        * rendering/style/StylePendingImage.h:
        (WebCore::StylePendingImage::image):
        * rendering/svg/RenderSVGImage.cpp:
        (WebCore::RenderSVGImage::paint):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76571 268f45cc-cd09-0410-ab3c-d52691b4dbfc