Enable compositing of scrolling content on low-DPI when LCD text will be maintained

third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt

Index: third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt
diff --git a/third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt b/third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt
index fcd89a27eeb3130b03f712c3c0b467ecaef6bdef..8c722eebe30dec3ce411a912ee135f3f133689d7 100644
--- a/third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt
+++ b/third_party/WebKit/LayoutTests/paint/invalidation/flexbox/scrollbars-changed-expected.txt
@@ -7,31 +7,89 @@
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
-      "paintInvalidations": [
+      "children": [
         {
-          "object": "LayoutBlockFlow DIV id='dynamic' class='content'",
-          "rect": [0, 0, 185, 30],
-          "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutBlockFlow DIV id='scroller'",
-          "rect": [185, 0, 15, 100],
-          "reason": "scroll"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [0, 5, 15, 15],
-          "reason": "full"
+          "name": "LayoutBlockFlow DIV id='scroller'",
+          "bounds": [200, 100],
+          "shouldFlattenTransform": false,
+          "drawsContent": true,
+          "backgroundColor": "#808080",
+          "children": [
+            {
+              "name": "Scrolling Layer",
+              "bounds": [185, 100],
+              "shouldFlattenTransform": false,
+              "children": [
+                {
+                  "name": "Scrolling Contents Layer",
+                  "bounds": [185, 210],
+                  "contentsOpaque": true,
+                  "drawsContent": true,
+                  "paintInvalidations": [
+                    {
+                      "object": "LayoutBlockFlow DIV id='dynamic' class='content'",
+                      "rect": [0, 0, 185, 30],
+                      "reason": "forced by layout"
+                    },
+                    {
+                      "object": "LayoutText #text",
+                      "rect": [0, 5, 15, 15],
+                      "reason": "full"
+                    }
+                  ]
+                }
+              ]
+            },
+            {
+              "name": "Overflow Controls Host Layer",
+              "bounds": [200, 100],
+              "children": [
+                {
+                  "name": "Vertical Scrollbar Layer",
+                  "position": [185, 0],
+                  "bounds": [15, 100],
+                  "paintInvalidations": [
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 210],
+                      "reason": "full"
+                    },
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 210],
+                      "reason": "full"
+                    },
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 100],
+                      "reason": "full"
+                    },
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 100],
+                      "reason": "full"
+                    },
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 100],
+                      "reason": "full"
+                    },
+                    {
+                      "object": "Vertical Scrollbar Layer",
+                      "rect": [0, 0, 15, 100],
+                      "reason": "full"
+                    }
+                  ]
+                }
+              ]
+            }
+          ]
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
-      "object": "VerticalScrollbar",
-      "reason": "scroll"
-    },
-    {
       "object": "LayoutBlockFlow DIV id='dynamic' class='content'",
       "reason": "forced by layout"
     },