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

third_party/WebKit/LayoutTests/compositing/layer-creation/fixed-position-nonscrollable-body-mismatch-containers-expected.txt

 Even though the fixed-position element's container is nonscrollable, it should still be composited because one of its ancestors is scrolling.
 
 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
@@ skipping 29 matching lines @@
       "position": [286, 1],
       "bounds": [15, 285]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [286, 286],
       "bounds": [15, 15],
       "drawsContent": true
     },
     {
+      "name": "Decoration Layer",
+      "bounds": [302, 302],
+      "drawsContent": true
+    },
+    {
       "name": "LayoutBlockFlow (positioned) DIV class='fixed lime box'",
       "position": [10, 100],
       "bounds": [100, 100],
       "contentsOpaque": true,
       "drawsContent": true,
       "backgroundColor": "#00FF00"
     }
   ]
 }