third_party/web_platform_tests/html/webappapis/animation-frames/callback-multicalls.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>AnimationTiming Test: multiple calls to requestAnimationFrame with the same callback</title>
<link rel="author" title="Intel" href="http://www.intel.com">
<link rel="help" href="https://html.spec.whatwg.org/multipage/#dom-window-requestanimationframe">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="log"></div>
<script>

  async_test(function(t) {
    var counter = 0;
    window.requestAnimationFrame(callback);

    function callback() {
      ++counter;
      if (counter == 2) {
        t.done();
      } else {
        window.requestAnimationFrame(callback);
      }
    };

  }, "Check that multiple calls to requestAnimationFrame with the same callback will result in multiple entries being in the list with that same callback.");

</script>