layer-position-with-outline.html | Explore in Territory

<!DOCTYPE html>
<script src="../../resources/run-after-layout-and-paint.js"></script>
<style>

.a { }
#f {
  position: absolute;
  left: 120px;
  top: 120px;
  width: 250px;
  height: 250px;
  border: 0;
  outline: 100px solid #fc8;
}

</style>
<div class="a"></div>
<iframe id="f" srcdoc="
  <style>
    body { will-change: transform; }
    #b { height: 200px; background: blue; }
  </style>
  <div id=b></div>"></iframe>
<script>

if (window.testRunner)
  testRunner.waitUntilDone();
onload = () => {
  var a = document.querySelector(".a");
  var f = document.querySelector("#f");
  var b = f.contentWindow.document.querySelector("#b");
  runAfterLayoutAndPaint(() => {

    // Invalidate main frame lifecycle without affecting compositing.
    a.className = "";

    // Invalidate child frame compositing state.
    b.style.opacity = "0.2";

  }, true);
};

</script>

chromium/third_party/blink/web_tests/compositing/iframes/layer-position-with-outline.html