Fix the bug that negative outline-offset is covered up by composited

third_party/WebKit/LayoutTests/paint/invalidation/compositing/updating-scrolling-content-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow DIV id='scroller'",
@@ skipping 38 matching lines @@
           "rect": [0, 0, 15, 185],
           "reason": "full"
         }
       ]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [185, 185],
       "bounds": [15, 15],
       "drawsContent": true
+    },
+    {
+      "name": "Decoration Layer",
+      "bounds": [200, 200],
+      "drawsContent": true
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutBlockFlow DIV id='indicator'",
       "reason": "style change"
     }
   ]
 }