Before:
{
  "layers": [
    {
      "name": "Scrolling background of LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutNGBlockFlow (positioned) DIV class='fixed'",
      "bounds": [30, 30],
      "contentsOpaque": true,
      "backgroundColor": "#0000FF",
      "transform": 2
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [10, 10, 0, 1]
      ]
    },
    {
      "id": 2,
      "parent": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [8, 100, 0, 1]
      ]
    }
  ]
}

After scroll:
{
  "layers": [
    {
      "name": "Scrolling background of LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutNGBlockFlow (positioned) DIV class='fixed'",
      "bounds": [30, 30],
      "contentsOpaque": true,
      "backgroundColor": "#0000FF",
      "transform": 2
    },
    {
      "name": "LayoutNGBlockFlow (relative positioned) DIV class='overlapped'",
      "position": [8, 102],
      "bounds": [40, 40],
      "contentsOpaque": true,
      "backgroundColor": "#FFA500",
      "transform": 1
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [10, 10, 0, 1]
      ]
    },
    {
      "id": 2,
      "parent": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [8, 100, 0, 1]
      ]
    }
  ]
}