Override repaintTreeAfterLayout for RenderSVGModelObject

RenderSVGModelObject needs to have an overload for said method, because
it inherits directly from RenderObject.
Also make sure RenderSVGBlock disables use of LayoutState.

BUG=369486

Review URL: https://codereview.chromium.org/260963012

git-svn-id: svn://svn.chromium.org/blink/trunk@173372 bbb929c8-8fbe-4397-9dbb-9b2b20218538