s how to mirror content to an external display
      while presenting to a VRDisplay.
    -->

    <style>
      #webgl-canvas {
        box-sizing: border-box;
        height: 100%;
        left: 0;
        margin: 0;
        position: absolute;
        top: 0;
        width: 100%;
      }
    </style>

    <!-- This entire block in only to facilitate dynamically enabling and
    disabling the WebVR polyfill, and is not necessary for most WebVR apps.
    If you want to use the polyfill in your app, just in