Factor out common code from RenderSVGResource*::postApplyResource

Factor the fill/stroke code out of the various paint-server
RenderSVGResource subclasses and move it to SVGRenderSupport.

Review URL: https://codereview.chromium.org/571463002

git-svn-id: svn://svn.chromium.org/blink/trunk@181907 bbb929c8-8fbe-4397-9dbb-9b2b20218538