Paint collapsed borders of a table as one display item

third_party/WebKit/LayoutTests/paint/invalidation/table-section-repaint-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
           "object": "LayoutTableCell TD class='half'",
@@ skipping 154 matching lines @@
     {
       "object": "LayoutTableRow TR",
       "reason": "location change"
     },
     {
       "object": "LayoutTableCell TD class='red half'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutTable TABLE",
+      "reason": "style change"
+    },
+    {
+      "object": "LayoutTable TABLE",
       "reason": "incremental"
     },
     {
       "object": "LayoutTableRow TR",
       "reason": "location change"
     },
     {
       "object": "LayoutTableCell TD class='half'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutTableRow TR",
       "reason": "location change"
     },
     {
       "object": "LayoutTableCell TD class='half'",
       "reason": "bounds change"
     }
   ]
 }