CASE 1, original layer tree
{
  "layers": [
    {
      "name": "LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "Squashing Containment Layer",
      "drawsContent": false
    },
    {
      "name": "LayoutBlockFlow (positioned) DIV class='composited box behind'",
      "bounds": [100, 100],
      "contentsOpaque": true,
      "backgroundColor": "#0000FF",
      "transform": 1
    },
    {
      "name": "Squashing Layer (first squashed layer: LayoutBlockFlow (positioned) DIV class='box middle')",
      "position": [4, 4],
      "bounds": [276, 276]
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [100, 100, 0, 1]
      ],
      "flattenInheritedTransform": false
    }
  ]
}
CASE 2, hovering over the outer div
{
  "layers": [
    {
      "name": "LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "Squashing Containment Layer",
      "drawsContent": false
    },
    {
      "name": "LayoutBlockFlow (positioned) DIV class='composited box behind'",
      "bounds": [100, 100],
      "contentsOpaque": true,
      "backgroundColor": "#0000FF",
      "transform": 1
    },
    {
      "name": "Squashing Layer (first squashed layer: LayoutBlockFlow (positioned) DIV class='box middle')",
      "position": [4, 4],
      "bounds": [276, 276],
      "paintInvalidations": [
        {
          "object": "LayoutBlockFlow (positioned) DIV class='box middle'",
          "rect": [0, 0, 132, 132],
          "reason": "style change"
        }
      ]
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [100, 100, 0, 1]
      ],
      "flattenInheritedTransform": false
    }
  ],
  "objectPaintInvalidations": [
    {
      "object": "LayoutBlockFlow (positioned) DIV class='box middle'",
      "reason": "style change"
    }
  ]
}
CASE 3, hovering over the inner div
{
  "layers": [
    {
      "name": "LayoutView #document",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "Squashing Containment Layer",
      "drawsContent": false
    },
    {
      "name": "LayoutBlockFlow (positioned) DIV class='composited box behind'",
      "bounds": [100, 100],
      "contentsOpaque": true,
      "backgroundColor": "#0000FF",
      "transform": 1
    },
    {
      "name": "Squashing Layer (first squashed layer: LayoutBlockFlow (positioned) DIV class='box middle')",
      "position": [4, 4],
      "bounds": [276, 276],
      "paintInvalidations": [
        {
          "object": "LayoutBlockFlow (positioned) DIV class='box middle'",
          "rect": [0, 0, 132, 132],
          "reason": "style change"
        },
        {
          "object": "LayoutBlockFlow (positioned) DIV class='smallbox'",
          "rect": [26, 28, 71, 72],
          "reason": "style change"
        }
      ]
    }
  ],
  "transforms": [
    {
      "id": 1,
      "transform": [
        [1, 0, 0, 0],
        [0, 1, 0, 0],
        [0, 0, 1, 0],
        [100, 100, 0, 1]
      ],
      "flattenInheritedTransform": false
    }
  ],
  "objectPaintInvalidations": [
    {
      "object": "LayoutBlockFlow (positioned) DIV class='box middle'",
      "reason": "style change"
    },
    {
      "object": "LayoutBlockFlow (positioned) DIV class='smallbox'",
      "reason": "style change"
    }
  ]
}