Prepare RenderLayer/RenderLayerBacking for RenderSVGModelObject support: SVG container repainting / viewport clipping need a few exceptions (see patch) + add a clipPath stub, since it logically belongs to painting related layer changes.
Created attachment 451016 [details] Patch, v1
Created attachment 451032 [details] Patch, v2
<rdar://problem/88860920>
Committed r290008 (247394@trunk): <https://commits.webkit.org/247394@trunk>