<!DOCTYPE html>
<style>
.x { background-color: yellow; }
</style>
<script src="util.js"></script>
<script>
window.onload = function() {
  let roots = [];
  for (let i = 0; i < 200; i++) {
    let root = document.createElement("div");
    roots.push(root);
    document.body.appendChild(root);
  }
  flush_layout(roots[0]);
  perf_start();
  for (x in ["x", "", "x"]) {
    for (let root of roots) {
      root.className = x;
    }
  }
  flush_style(roots[0]);
  perf_finish();
};
</script>
<body></body>
