chromium/third_party/blink/perf_tests/events/hit-test-lots-of-layers.html

<!DOCTYPE html>
<style>
body {
    display: flex;
    flex-wrap: wrap;
}
div {
    height: 1px;
    width: 200px;
    position: relative;
    background-color: green;
}
</style>
<body>
<script src="../resources/runner.js"></script>
<script>
var count = 5000;
function setupTest() {
    for (var i = 0; i < count; ++i)
        document.body.appendChild(document.createElement("div"));
}

setupTest();

function test() {
    for (var i = 0; i < 1000; i++) {
      var x = 600 * Math.random();
      var y = 400 * Math.random();
      var el = document.elementFromPoint(x, y);
    }
}

PerfTestRunner.measureRunsPerSecond({
description: "Measures hit test performance with many layers.",
run: test
});
</script>