Put SVGResourceContainer subtypes into their own property trees.

third_party/WebKit/LayoutTests/paint/invalidation/svg/clip-path-child-changes-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutSVGContainer g",
           "rect": [0, 0, 200, 200],
           "reason": "full"
-        },
-        {
-          "object": "LayoutSVGPath path",
-          "rect": [0, 0, 200, 200],
-          "reason": "subtree"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutSVGPath path",
       "reason": "subtree"
     },
     {
       "object": "LayoutSVGContainer g",
       "reason": "full"
     }
   ]
 }