Only promote opaque scrollers which are stacking contexts.

third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt

Index: third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt
diff --git a/third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt b/third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt
index 3a706be0e11fa67d2205dd085d14fe948429bf09..76dbf0315b6001aaddd91b0c0b4aeddfbc53ae76 100644
--- a/third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt
+++ b/third_party/WebKit/LayoutTests/compositing/layer-creation/scroll-partial-update-expected.txt
@@ -21,34 +21,6 @@ scroll me
       "position": [10, 8],
       "bounds": [400, 204],
       "drawsContent": true
-    },
-    {
-      "name": "LayoutBlockFlow DIV id='scroller'",
-      "position": [202, 10],
-      "bounds": [200, 200],
-      "shouldFlattenTransform": false,
-      "drawsContent": true,
-      "backgroundColor": "#FFFF00"
-    },
-    {
-      "name": "Scrolling Layer",
-      "bounds": [185, 200],
-      "shouldFlattenTransform": false
-    },
-    {
-      "name": "Scrolling Contents Layer",
-      "bounds": [185, 400],
-      "contentsOpaque": true,
-      "drawsContent": true
-    },
-    {
-      "name": "Overflow Controls Host Layer",
-      "bounds": [200, 200]
-    },
-    {
-      "name": "Vertical Scrollbar Layer",
-      "position": [185, 0],
-      "bounds": [15, 200]
     }
   ]
 }