Simplify ObjectPaintInvalidatorW/C::computePaintInvalidationReason()

third_party/WebKit/LayoutTests/platform/mac/paint/invalidation/selection/invalidation-rect-includes-newline-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutText #text",
           "rect": [8, 8, 48, 33],
-          "reason": "full"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [8, 8, 48, 32],
-          "reason": "selection"
+          "reason": "bounds change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow HTML",
       "reason": "selection"
     },
     {
       "object": "LayoutBlockFlow BODY",
       "reason": "selection"
     },
     {
       "object": "LayoutBlockFlow DIV id='container'",
       "reason": "selection"
     },
     {
       "object": "LayoutText #text",
-      "reason": "selection"
+      "reason": "bounds change"
     },
     {
       "object": "InlineTextBox 'xx'",
-      "reason": "selection"
+      "reason": "bounds change"
     },
     {
       "object": "InlineTextBox 'y'",
-      "reason": "selection"
-    },
-    {
-      "object": "LayoutText #text",
-      "reason": "full"
-    },
-    {
-      "object": "InlineTextBox 'xx'",
-      "reason": "full"
-    },
-    {
-      "object": "InlineTextBox 'y'",
-      "reason": "full"
+      "reason": "bounds change"
     }
   ]
 }