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

third_party/WebKit/LayoutTests/platform/win/compositing/overflow/textarea-scroll-touch-expected.txt

   
 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true
     },
     {
@@ skipping 25 matching lines @@
       "position": [190, 1],
       "bounds": [15, 109]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [190, 110],
       "bounds": [15, 15],
       "drawsContent": true
     },
     {
+      "name": "Decoration Layer",
+      "bounds": [206, 126],
+      "drawsContent": true
+    },
+    {
       "name": "LayoutTextControl TEXTAREA",
       "position": [248, 18],
       "bounds": [206, 126],
       "shouldFlattenTransform": false,
       "drawsContent": true,
       "backgroundColor": "#CCCCCC"
     },
     {
       "name": "Scrolling Layer",
       "position": [1, 1],
@@ skipping 13 matching lines @@
     {
       "name": "Vertical Scrollbar Layer",
       "position": [190, 1],
       "bounds": [15, 109]
     },
     {
       "name": "Scroll Corner Layer",
       "position": [190, 110],
       "bounds": [15, 15],
       "drawsContent": true
+    },
+    {
+      "name": "Decoration Layer",
+      "bounds": [206, 126],
+      "drawsContent": true
     }
   ]
 }