Put SVGResourceContainer subtypes into their own property trees.

third_party/WebKit/LayoutTests/paint/invalidation/svg/relative-sized-use-on-symbol-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow div id='contentBox'",
           "rect": [8, 50, 402, 402],
           "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutSVGPath path",
-          "rect": [16, 57, 136, 137],
-          "reason": "bounds change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow div id='contentBox'",
       "reason": "forced by layout"
     },
     {
       "object": "RootInlineBox",
       "reason": "forced by layout"
     },
     {
       "object": "LayoutSVGRoot svg",
       "reason": "forced by layout"
     },
     {
-      "object": "LayoutSVGPath path",
-      "reason": "bounds change"
-    },
-    {
       "object": "LayoutSVGContainer use",
       "reason": "bounds change"
     },
     {
       "object": "LayoutSVGViewportContainer svg id='gamesBorder'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutSVGPath path",
       "reason": "bounds change"
     }
   ]
 }