imperative-api-detail-summary-large.html

<!doctype html>
<script src="../resources/runner.js"></script>
<details id="details">
  <summary id="summary">summary</summary>
</details>
<summary id="summary1">added-summary1</summary>
<summary id="summary2">added-summary2</summary>
<script>
  const host = document.querySelector("#details");
  const sum = document.querySelector("#summary");
  const sum1 = document.querySelector("#summary1");
  const sum2 = document.querySelector("#summary2");
  window.onload = function() {
    for (let i = 0; i < 100; i++) {
      host.appendChild(document.createElement("summary"));
    }
    PerfTestRunner.measureTime({
      description: "Measure performance of built-in detail element when summary element is inserted when the child node is over 100",
      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-detail-summary-large.html