imperative-api-custom-detail-summary.html

<!DOCTYPE html>
<script src="../resources/runner.js"></script>
<script src="custom-detail-summary.js"></script>
<my-detail id="my-detail">
  <my-summary id="my-summary">summary</my-summary>
</my-detail>
<my-summary id="my-summary1">added-summary1</my-summary>
<my-summary id="my-summary2">added-summary2</my-summary>
<script>
  const host = document.querySelector("#my-detail");
  const sum = document.querySelector("#my-summary");
  const sum1 = document.querySelector("#my-summary1");
  const sum2 = document.querySelector("#my-summary2");
  window.onload = function() {
    PerfTestRunner.measureTime({
      description: "Measure performance of my-detail element in manual-slotting mode in shadow root when my-summary element is inserted.",
      run: function() {
        const start = PerfTestRunner.now();
        for (let i = 0; i < 100; i++) {
          host.appendChild(sum1);
          host.insertBefore(sum2, sum);
          PerfTestRunner.forceLayout();
          sum1.remove();
          sum2.remove();
          PerfTestRunner.forceLayout();
        }

        return PerfTestRunner.now() - start;
      }
    });
  }
</script>

chromium/third_party/blink/perf_tests/shadow_dom/imperative-api-custom-detail-summary.html