[css-grid] Only force full invalidation when grid item data change

third_party/WebKit/LayoutTests/fast/repaint/justify-content-position-change-grid-expected.txt

 {
   "name": "Content Root Layer",
   "bounds": [800, 600],
   "children": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "paintInvalidations": [
         {
-          "object": "LayoutGrid DIV id='container'",
-          "rect": [0, 52, 300, 200],
-          "reason": "style change"
-        },
-        {
           "object": "LayoutBlockFlow DIV class='item'",
           "rect": [250, 52, 50, 200],
           "reason": "bounds change"
         },
         {
           "object": "LayoutBlockFlow DIV class='item'",
           "rect": [200, 52, 50, 200],
           "reason": "bounds change"
         },
         {
@@ skipping 14 matching lines @@
         {
           "object": "LayoutBlockFlow DIV class='item'",
           "rect": [0, 52, 50, 200],
           "reason": "bounds change"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
-      "object": "LayoutGrid DIV id='container'",
-      "reason": "style change"
-    },
-    {
       "object": "LayoutBlockFlow DIV class='item'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "location change"
     },
     {
       "object": "LayoutBlockFlow DIV class='item'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "location change"
     },
     {
       "object": "LayoutBlockFlow DIV class='item'",
       "reason": "bounds change"
     },
     {
       "object": "LayoutBlockFlow DIV",
       "reason": "location change"
     }
   ]
 }