<!DOCTYPE html>

<html>
<head>
  <style>
      .fixed {
          position: fixed;
          width: 10px;
          height: 10px;
          background-color: silver;
          transform: translateX(0); /* Defeat clip to viewport */
      }
  </style>
  <script type="text/javascript">
    if (window.testRunner && window.internals) {
      testRunner.dumpAsText();
      internals.settings.setAcceleratedCompositingForFixedPositionEnabled(true);

      addEventListener("load", function() {
        let layers1 = internals.layerTreeAsText(document);
        document.getElementById("fixed1").style.top = "50px";
        document.getElementById("fixed2").style.height = "10px";

        let layers2 = internals.layerTreeAsText(document);
        document.getElementById("fixed1").style.top = "-100px";
        document.getElementById("fixed2").style.height = "0px";

        let layers3 = internals.layerTreeAsText(document);
        document.getElementById("layerTree1").innerText = layers1;
        document.getElementById("layerTree2").innerText = layers2;
        document.getElementById("layerTree3").innerText = layers3;
      }, false);
    }
  </script>
</head>

<body>
  Layer tree when the fixed elements are out-of-view (should be blank):
  <pre id="layerTree1"></pre>
  Layer tree when the fixed elements are in-view (both fixed elements should have layers):
  <pre id="layerTree2"></pre>
  Layer tree when the fixed elements are out-of-view again (should be blank):
  <pre id="layerTree3"></pre>
  <div id="fixed1" class="fixed" style="top: -100px; left: 100px;"></div>
  <div id="fixed2" class="fixed" style="top: 100px; left: 100px; height: 0px"></div>
</body>
</html>