Initial
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [785, 626],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutBlockFlow DIV class='composited container'",
      "bounds": [749, 145],
      "drawsContent": false,
      "transform": 1
    },
    {
      "name": "LayoutBlockFlow DIV class='composited hidden container'",
      "position": [-4, -4],
      "bounds": [757, 153],
      "drawsContent": false,
      "transform": 2
    },
    {
      "name": "LayoutImage IMG class='visible composited box'",
      "bounds": [100, 100],
      "transform": 3
    },
    {
      "name": "ContentsLayer for Vertical Scrollbar Layer",
      "position": [785, 0],
      "bounds": [15, 600],
      "contentsOpaque": true
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 10, 0, 1]
      ]
    },
    {
      "id": 2,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 320, 0, 1]
      ]
    },
    {
      "id": 3,
      "parent": 2,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    }
  ]
}

After step 1
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [785, 1670],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutBlockFlow DIV class='composited container'",
      "bounds": [749, 145],
      "drawsContent": false,
      "transform": 1
    },
    {
      "name": "LayoutImage IMG class='hidden composited box'",
      "bounds": [100, 100],
      "transform": 2
    },
    {
      "name": "LayoutBlockFlow DIV class='composited hidden container'",
      "position": [-4, -4],
      "bounds": [757, 153],
      "drawsContent": false,
      "transform": 3
    },
    {
      "name": "LayoutImage IMG class='visible composited box'",
      "bounds": [100, 100],
      "transform": 4
    },
    {
      "name": "ContentsLayer for Vertical Scrollbar Layer",
      "position": [785, 0],
      "bounds": [15, 600],
      "contentsOpaque": true
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 10, 0, 1]
      ]
    },
    {
      "id": 2,
      "parent": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    },
    {
      "id": 3,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 320, 0, 1]
      ]
    },
    {
      "id": 4,
      "parent": 3,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    }
  ]
}

After step 2
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [785, 2953],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutBlockFlow DIV class='composited container'",
      "bounds": [749, 145],
      "drawsContent": false,
      "transform": 1
    },
    {
      "name": "LayoutImage IMG class='hidden composited box'",
      "bounds": [100, 100],
      "transform": 2
    },
    {
      "name": "LayoutBlockFlow DIV class='composited hidden container'",
      "position": [-4, -4],
      "bounds": [757, 153],
      "transform": 3
    },
    {
      "name": "LayoutImage IMG class='composited box'",
      "bounds": [100, 100],
      "transform": 4
    },
    {
      "name": "LayoutBlockFlow DIV class='composited hidden container'",
      "position": [-4, -4],
      "bounds": [757, 153],
      "drawsContent": false,
      "transform": 5
    },
    {
      "name": "LayoutImage IMG class='visible composited box'",
      "bounds": [100, 100],
      "transform": 6
    },
    {
      "name": "ContentsLayer for Vertical Scrollbar Layer",
      "position": [785, 0],
      "bounds": [15, 600],
      "contentsOpaque": true
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 10, 0, 1]
      ]
    },
    {
      "id": 2,
      "parent": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    },
    {
      "id": 3,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 165, 0, 1]
      ]
    },
    {
      "id": 4,
      "parent": 3,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    },
    {
      "id": 5,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [18, 320, 0, 1]
      ]
    },
    {
      "id": 6,
      "parent": 5,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [20, 20, 0, 1]
      ]
    }
  ]
}