Layer tree when the fixed elements are out-of-view (should have just a root layer):
{
  "bounds": [785, 4016],
  "children": [
    {
      "bounds": [785, 4016],
      "contentsOpaque": true,
      "drawsContent": true
    }
  ]
}
Layer tree when the fixed elements are in-view (both fixed elements should have layers):
{
  "bounds": [785, 4016],
  "children": [
    {
      "bounds": [785, 4016],
      "contentsOpaque": true,
      "drawsContent": true,
      "children": [
        {
          "position": [100, 50],
          "bounds": [10, 10],
          "contentsOpaque": true,
          "drawsContent": true,
          "backgroundColor": "#C0C0C0"
        },
        {
          "position": [100, 100],
          "bounds": [10, 10],
          "contentsOpaque": true,
          "drawsContent": true,
          "backgroundColor": "#C0C0C0"
        }
      ]
    }
  ]
}
Layer tree when the fixed elements are out-of-view again (should have just a root layer):
{
  "bounds": [785, 4016],
  "children": [
    {
      "bounds": [785, 4016],
      "contentsOpaque": true,
      "drawsContent": true
    }
  ]
}