First dump layer tree:
{
  "layers": [
    {
      "name": "Scrolling background of LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    }
  ]
}

Second dump layer tree:
{
  "layers": [
    {
      "name": "Scrolling background of LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutBlockFlow (relative positioned, children-inline) DIV id='child' class='child'",
      "bounds": [250, 100],
      "contentsOpaque": true,
      "backgroundColor": "#008000",
      "transform": 3
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [8, 8, 0, 1]
      ]
    },
    {
      "id": 2,
      "parent": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [121, 41, 0, 1]
      ]
    },
    {
      "id": 3,
      "parent": 2,
      "transform": [
        [0.707106781186548, 0, -0.707106781186548, 0.00117851130197758],
        [0, 1, 0, 0],
        [0.707106781186548, 0, 0.707106781186548, -0.00117851130197758],
        [-50, 10, 100, 0.833333333333333]
      ],
      "origin": [125, 50]
    }
  ]
}

Third dump layer tree:
{
  "layers": [
    {
      "name": "Scrolling background of LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    }
  ]
}