Simplify ObjectPaintInvalidatorW/C::computePaintInvalidationReason()

third_party/WebKit/LayoutTests/paint/invalidation/svg/marker-viewBox-changes-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutSVGContainer g",
           "rect": [90, 95, 98, 98],
           "reason": "bounds change"
         },
         {
           "object": "LayoutSVGPath path id='go'",
           "rect": [90, 95, 98, 98],
           "reason": "full"
         },
         {
           "object": "LayoutSVGRoot svg",
           "rect": [90, 95, 98, 98],
           "reason": "bounds change"
         },
         {
           "object": "LayoutSVGRect rect",
           "rect": [0, 0, 10, 10],
-          "reason": "full"
+          "reason": "bounds change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutSVGRoot svg",
       "reason": "bounds change"
     },
     {
       "object": "LayoutSVGResourceMarker marker id='markerStart'",
       "reason": "full"
     },
     {
       "object": "LayoutSVGRect rect",
-      "reason": "full"
+      "reason": "bounds change"
     },
     {
       "object": "LayoutSVGContainer g",
       "reason": "bounds change"
     },
     {
       "object": "LayoutSVGPath path id='go'",
       "reason": "full"
     }
   ]
 }