composite-scrollable-fixed-position-when-descendants-composite.html

<!doctype HTML>
<head>
  <script src="../resources/testharness.js"></script>
  <script src="../resources/testharnessreport.js"></script>
</head>

<div style="position: fixed; width: 100px; height: 100px; background: lightgray">
  <div style="will-change: transform; margin: 50px; width: 50px; height: 50px; background: lightblue"></div>
</div>

<div id="force_document_scroll" style="height: 5000px;"></div>

<script>
  test(function() {
    assert_not_equals(window.internals, null, 'This test requires window.internals');
    var layers_text = internals.layerTreeAsText(document);
    var layers = JSON.parse(layers_text);
    assert_equals(layers['layers'].length, 4);
  }, 'Having a composited child should be a position:fixed compositing trigger and should result in the fixed element getting a layer.');
</script>

chromium/third_party/blink/web_tests/compositing/composite-scrollable-fixed-position-when-descendants-composite.html