<!DOCTYPE html>

<html>
<head>
  <style>
    .fixed {
      position: fixed;
      z-index: 1;
    }

    .absolute {
        position: absolute;
    }

    .unscrollable {
        overflow-x: hidden;
        overflow-y: hidden;
    }

    .box {
        top: 10px;
        left: 10px;
        width: 100px;
        height: 100px;
    }

    .red {
        background-color: red;
    }

    .lime {
        background-color: lime;
    }

    .composited {
        transform: translatez(0);
    }
  </style>
</head>

<body class="unscrollable">
  <div style="height: 4000px">
    <!-- This iframe should have no additional layers, because the body is unscrollable and there is
         no need to composite the green fixed-position layer. -->
    <pre id="layertree"></pre>
  </div>

  <!-- This should not be composited -->
  <div class="fixed lime box"></div>
</body>
</html>