Simplify incremental paint invalidation

third_party/WebKit/LayoutTests/paint/invalidation/fixed-under-composited-absolute-scrolled-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [785, 2001],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV id='absolute'",
       "position": [0, 400],
       "bounds": [100, 1601],
       "drawsContent": true,
       "backfaceVisibility": "hidden",
       "backgroundColor": "#FF0000",
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow (positioned) DIV id='fixed'",
-          "rect": [0, 100, 100, 100],
+          "rect": [0, 0, 100, 200],
           "reason": "incremental"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow (positioned) DIV id='fixed'",
       "reason": "incremental"
     }
   ]
 }