Paint collapsed borders of a table as one display item

third_party/WebKit/LayoutTests/paint/invalidation/table-outer-border-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutTable TABLE id='table'",
@@ skipping 77 matching lines @@
     },
     {
       "object": "LayoutTableSection TBODY",
       "reason": "layoutObject removal"
     },
     {
       "object": "LayoutTable TABLE id='table'",
       "reason": "layoutObject removal"
     },
     {
-      "object": "LayoutTableCell TD",
-      "reason": "style change"
-    },
-    {
-      "object": "LayoutTableCell TD",
-      "reason": "style change"
-    },
-    {
       "object": "LayoutTable TABLE id='table' class='green'",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutTableSection TBODY",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutTableRow TR",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutTableCell TD",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutTableRow TR",
       "reason": "layoutObject insertion"
     },
     {
       "object": "LayoutTableCell TD",
       "reason": "layoutObject insertion"
     }
   ]
 }