Fix issue when background changes painting target layer

third_party/WebKit/LayoutTests/paint/invalidation/destroy-composited-scrollbar-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV",
       "position": [0, 100],
       "bounds": [200, 200],
       "contentsOpaque": true,
       "drawsContent": true,
       "backgroundColor": "#0000FF",
       "paintInvalidations": [
         {
           "object": "LayoutBlockFlow (positioned) DIV",
           "rect": [0, 0, 200, 200],
           "reason": "full"
         },
         {
           "object": "LayoutBlockFlow (positioned) DIV",
+          "rect": [0, 0, 200, 200],
+          "reason": "full"
+        },
+        {
+          "object": "LayoutBlockFlow (positioned) DIV",
           "rect": [185, 0, 15, 200],
           "reason": "scroll"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow (positioned) DIV",
       "reason": "scroll"
     }
   ]
 }