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

third_party/WebKit/LayoutTests/compositing/overflow/accelerated-overflow-scroll-should-not-affect-perspective-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow (positioned) DIV class='container'",
@@ skipping 63 matching lines @@
     {
       "name": "Vertical Scrollbar Layer",
       "position": [185, 0],
       "bounds": [15, 185]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [185, 185],
       "bounds": [15, 15],
       "drawsContent": true
+    },
+    {
+      "name": "Decoration Layer",
+      "bounds": [200, 200],
+      "drawsContent": true
     }
   ]
 }