chromium/third_party/blink/perf_tests/css/HasInvalidationFiltering.html

<!DOCTYPE html>
<html>
<head>
<script src="../resources/runner.js"></script>
<style>
  div { color: grey }
  .a:has(.b) { color: red }
  .c:has(.d) { color: green }
  .e:has(.f) .g { color: blue }
  .e:has(.h) .i { color: navy }
  .e:has(.f.h) .j { color: lightgreen }
</style>
</head>
<body>
<div id=container class="a e"></div>
<script>

function addChildren(element, numChildren, idPrefix)
{
  for (var i = 0; i < numChildren; i++) {
    var child = document.createElement("div");
    child.id = idPrefix  + i;
    element.appendChild(child);
  }
}

function makeTree(element, depth, fanOut, idPrefix)
{
  if (depth <= 0)
    return;
  addChildren(element, fanOut, idPrefix);
  for (var child = element.firstChild; child.nextSibling; child = child.nextSibling)
    makeTree(child, depth - 1, fanOut, child.id);
  if (child)
    makeTree(child, depth - 1, fanOut, child.id);
}

makeTree(container, 3, 5, "child");

child21.classList.add('g');
child22.classList.add('i')
child23.classList.add('j');
container.offsetHeight; // force recalc style

var runFunction = function()
{
  // this should not invalidate any element.
  child22.classList.toggle('d');
  container.offsetHeight; // force recalc style
  child22.classList.toggle('d');
  container.offsetHeight; // force recalc style

  // this should invalidate only #child21
  child22.classList.toggle('f');
  container.offsetHeight; // force recalc style
  child22.classList.toggle('f');
  container.offsetHeight; // force recalc style
}

PerfTestRunner.measureRunsPerSecond({
  description: "Measures performance of the :has() pseudo class invalidation filtering.",
  run: runFunction
});

</script>
</body>
</html>