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

third_party/WebKit/LayoutTests/compositing/layer-creation/fixed-position-in-fixed-overflow-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV class='overflow fixed'",
@@ skipping 21 matching lines @@
       "backgroundColor": "#FFFF00"
     },
     {
       "name": "Overflow Controls Host Layer",
       "bounds": [800, 600]
     },
     {
       "name": "Vertical Scrollbar Layer",
       "position": [785, 0],
       "bounds": [15, 600]
+    },
+    {
+      "name": "Decoration Layer",
+      "bounds": [800, 600],
+      "drawsContent": true
     }
   ]
 }