A <video> should not have a layer until playback begins.
This test can not be run manually, it requires testRunner.layerTreeAsText.

Case: No src, no poster
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    }
  ]
}


Case: Displaying poster
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [800, 600],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    }
  ]
}


Case: Displaying movie
{
  "layers": [
    {
      "name": "Scrolling Contents Layer",
      "bounds": [785, 813],
      "contentsOpaque": true,
      "backgroundColor": "#FFFFFF"
    },
    {
      "name": "LayoutVideo VIDEO",
      "bounds": [352, 288],
      "drawsContent": false,
      "transform": 1
    },
    {
      "name": "ContentsLayer for LayoutVideo VIDEO",
      "bounds": [352, 288],
      "transform": 1
    },
    {
      "name": "LayoutNGFlexibleBox (relative positioned) DIV class='sizing-small phase-ready state-scrubbing'",
      "bounds": [352, 288],
      "transform": 1
    },
    {
      "name": "Squashing Layer (first squashed layer: LayoutNGBlockFlow (positioned) DIV)",
      "bounds": [352, 288],
      "transform": 1
    },
    {
      "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],
        [8, 8, 0, 1]
      ]
    }
  ]
}