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

third_party/WebKit/LayoutTests/compositing/overflow/scroll-parent-absolute-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [785, 5516],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
       "name": "Squashing Containment Layer",
@@ skipping 32 matching lines @@
       "position": [485, 0],
       "bounds": [15, 485]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [485, 485],
       "bounds": [15, 15],
       "drawsContent": true
     },
     {
+      "name": "Decoration Layer",
+      "bounds": [500, 500],
+      "drawsContent": true
+    },
+    {
       "name": "Squashing Layer (first squashed layer: LayoutBlockFlow (positioned) DIV id='middle')",
       "position": [8, 8],
       "bounds": [400, 400],
       "drawsContent": true
     },
     {
       "name": "LayoutBlockFlow (relative positioned) DIV id='child'",
       "position": [8, 8],
       "bounds": [300, 300],
       "contentsOpaque": true,
       "drawsContent": true,
       "backfaceVisibility": "hidden",
       "backgroundColor": "#FFFF00"
     },
     {
       "name": "LayoutBlockFlow (relative positioned) DIV id='tall'",
       "position": [8, 8],
       "bounds": [20, 5000],
       "contentsOpaque": true,
       "drawsContent": true,
       "backgroundColor": "#FA8072",
       "hasScrollParent": true
     }
   ]
 }