<!DOCTYPE html>
<style>
.x { color: blue; }
.y { background-color: green; }
</style>
<script src="util.js"></script>
<script>
function find_leftmost(e) {
  while (e.firstChild) {
    e = e.firstChild;
  }
  return e;
}
window.onload = function() {
  document.head.appendChild(build_rule("div", 1, "{ color: blue; }", 100));
  let root = document.createElement("div");
  root.className = "root";
  root.appendChild(build_dom(50000, "div"));
  let leftmost = find_leftmost(root);
  document.body.appendChild(root);
  flush_layout(root);
  perf_start();
  document.body.className = "x";
  leftmost.className = "y";
  flush_style(root);
  perf_finish();
};
</script>
<body></body>
