Simplify ObjectPaintInvalidatorW/C::computePaintInvalidationReason()

third_party/WebKit/LayoutTests/platform/linux/paint/invalidation/svg/js-late-clipPath-creation-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutSVGContainer g id='content'",
           "rect": [16, 42, 784, 170],
-          "reason": "full"
+          "reason": "bounds change"
         },
         {
           "object": "LayoutSVGInlineText #text",
           "rect": [16, 42, 784, 170],
           "reason": "forced by layout"
         },
         {
           "object": "LayoutSVGText text",
           "rect": [16, 42, 784, 170],
           "reason": "style change"
@@ skipping 11 matching lines @@
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutSVGRoot svg id='svg-root'",
       "reason": "incremental"
     },
     {
       "object": "LayoutSVGContainer g id='content'",
-      "reason": "full"
+      "reason": "bounds change"
     },
     {
       "object": "LayoutSVGText text",
       "reason": "style change"
     },
     {
       "object": "RootInlineBox",
       "reason": "style change"
     },
     {
       "object": "LayoutSVGInlineText #text",
       "reason": "forced by layout"
     },
     {
       "object": "InlineTextBox 'Clipped. INVISIBLE.'",
       "reason": "forced by layout"
     },
     {
       "object": "LayoutSVGResourceClipper clipPath id='dynClip'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutSVGPath path",
       "reason": "layoutObject insertion"
     }
   ]
 }