Two tests in compositing/squashing fail with RLS:

  compositing/squashing/squash-above-fixed-1.html
  compositing/squashing/squash-above-fixed-3.html

Snippet of diff:

   "layers": [
     {
       "name": "LayoutView #document",
+      "bounds": [800, 600],
+      "backgroundColor": "#FFFFFF"
+    },
+    {
+      "name": "Scrolling Layer",
+      "bounds": [785, 600],
+      "drawsContent": false
+    },
+    {
+      "name": "Scrolling Contents Layer",
       "bounds": [785, 1400],
       "contentsOpaque": true,
       "backgroundColor": "#FFFFFF",
-      "paintInvalidations": [
-        {
-          "object": "LayoutBlockFlow (relative positioned) DIV id='paragraph-f' class='overlapping lime'",
-          "rect": [0, 500, 200, 100],
-          "reason": "subtree"
-        },
-        {
-          "object": "LayoutBlockFlow (relative positioned) DIV id='paragraph-e' class='overlapping cyan'",
-          "rect": [0, 200, 200, 100],
-          "reason": "subtree"
-        },
...

The insertion of Scrolling Layer and Scrolling Contents Layer is expected, but the missing "paintInvalidations" entries are not.