Put SVGResourceContainer subtypes into their own property trees.

third_party/WebKit/LayoutTests/paint/invalidation/svg/js-late-mask-and-object-creation-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
-          "object": "LayoutSVGRect rect",
-          "rect": [0, 0, 800, 300],
-          "reason": "layoutObject insertion"
-        },
-        {
           "object": "LayoutSVGContainer g id='content'",
           "rect": [0, 100, 800, 100],
           "reason": "became visible"
         },
         {
           "object": "LayoutSVGRect rect",
           "rect": [0, 100, 800, 100],
           "reason": "style change"
         }
       ]
@@ skipping 16 matching lines @@
       "object": "LayoutSVGResourceMasker mask id='dynMask'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutSVGRect rect",
       "reason": "layoutObject insertion"
     }
   ]
 }