Reviewed by Nikolas Zimmermann.

        SVG Pattern/Gradient clean-up
        https://bugs.webkit.org/show_bug.cgi?id=40205

        Transformations of SVG Patterns and Gradients can be bundeled.
        This calculation also needs just to be calculated once. It's not a great speed-up for most platforms,
        but a clean-up and preparation for new features like vectorEffects and others.
        Now, that we don't recalucluate the gradient and its transformations, it was necessary to add a way
        to transform alreday existing gradients on Cairo. This is done in the same way like Skia transforms
        gradients after they were created.
        
        This patch doesn't change functionality, so no new tests added.

        * platform/graphics/Gradient.cpp:
        * platform/graphics/cairo/GradientCairo.cpp:
        (WebCore::Gradient::setPlatformGradientSpaceTransform):
        * rendering/RenderSVGResourceGradient.cpp:
        (WebCore::RenderSVGResourceGradient::applyResource):
        * rendering/RenderSVGResourceGradient.h:
        * rendering/RenderSVGResourcePattern.cpp:
        (WebCore::RenderSVGResourcePattern::applyResource):
        (WebCore::RenderSVGResourcePattern::createTileImage):
        (WebCore::RenderSVGResourcePattern::buildPattern):
        * rendering/RenderSVGResourcePattern.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@60760 268f45cc-cd09-0410-ab3c-d52691b4dbfc