Simplify ObjectPaintInvalidatorW/C::computePaintInvalidationReason()

third_party/WebKit/LayoutTests/paint/invalidation/svg/feImage-target-attribute-change-with-use-indirection-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutSVGRect rect",
           "rect": [0, 0, 110, 110],
           "reason": "full"
         },
         {
           "object": "LayoutSVGContainer use id='use'",
           "rect": [0, 0, 100, 100],
-          "reason": "full"
+          "reason": "bounds change"
         },
         {
           "object": "LayoutSVGRect rect id='rect'",
           "rect": [0, 0, 100, 100],
           "reason": "full"
         },
         {
           "object": "LayoutSVGRect rect id='rect'",
           "rect": [0, 0, 100, 100],
           "reason": "layoutObject insertion"
@@ skipping 10 matching lines @@
     {
       "object": "LayoutSVGRect rect id='rect'",
       "reason": "layoutObject removal"
     },
     {
       "object": "LayoutSVGRect rect id='rect'",
       "reason": "full"
     },
     {
       "object": "LayoutSVGContainer use id='use'",
-      "reason": "full"
+      "reason": "bounds change"
     },
     {
       "object": "LayoutSVGRect rect id='rect'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutSVGRect rect",
       "reason": "full"
     }
   ]
 }