Paint collapsed borders of a table as one display item

third_party/WebKit/LayoutTests/paint/invalidation/table/cached-cell-append-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutTable TABLE",
-          "rect": [8, 59, 120, 5],
-          "reason": "incremental"
+          "rect": [8, 8, 120, 56],
+          "reason": "forced by layout"
         },
         {
           "object": "LayoutTableCell TD",
           "rect": [64, 8, 64, 56],
           "reason": "layoutObject insertion"
         },
         {
-          "object": "LayoutTable TABLE",
-          "rect": [65, 8, 63, 56],
-          "reason": "incremental"
-        },
-        {
           "object": "LayoutTableCell TD",
           "rect": [8, 8, 62, 56],
           "reason": "location change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
-      "object": "LayoutTableCell TD",
-      "reason": "style change"
-    },
-    {
-      "object": "LayoutTableCell TD",
-      "reason": "style change"
-    },
-    {
       "object": "LayoutTable TABLE",
-      "reason": "incremental"
+      "reason": "forced by layout"
     },
     {
       "object": "LayoutTableRow TR id='row'",
       "reason": "location change"
     },
     {
       "object": "LayoutTableCell TD",
       "reason": "location change"
     },
     {
       "object": "LayoutTableCell TD",
       "reason": "layoutObject insertion"
     }
   ]
 }