https://bugs.webkit.org/show_bug.cgi?id=124332

Reviewed by Andreas Kling.

To use TYPE_CASTS_BASE, define FILTER_TYPE_CASTS macro. Thanks to
it, static_cast<SVGFilter*> can be replaced by toSVGFilter().

No new tests, no behavior changes.

* platform/graphics/filters/Filter.h:
    Add isSVGFilter() to check if casting object is SVGFilter object.
(WebCore::Filter::isSVGFilter):
* rendering/svg/RenderSVGResourceFilterPrimitive.cpp:
(WebCore::RenderSVGResourceFilterPrimitive::determineFilterPrimitiveSubregion):
* svg/graphics/filters/SVGFEImage.cpp:
(WebCore::FEImage::determineAbsolutePaintRect):
(WebCore::FEImage::platformApplySoftware):
* svg/graphics/filters/SVGFilter.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159277 268f45cc-cd09-0410-ab3c-d52691b4dbfc