Simplify incremental paint invalidation

third_party/WebKit/LayoutTests/paint/invalidation/transform-disable-layoutstate-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow DIV",
           "rect": [58, 152, 500, 49],
           "reason": "incremental"
         },
         {
           "object": "LayoutBlockFlow DIV",
           "rect": [58, 256, 500, 45],
           "reason": "incremental"
-        },
-        {
-          "object": "LayoutBlockFlow DIV",
-          "rect": [58, 156, 500, 45],
-          "reason": "incremental"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "incremental"
     },
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "incremental"
     }
   ]
 }