third_party/web_platform_tests/dom/events/Event-dispatch-redispatch.html

<!DOCTYPE html>
<meta charset=urf-8>
<title>EventTarget#dispatchEvent(): redispatching a native event</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id=log></div>
<script>
async_test(function() {
  var event;
  document.addEventListener("DOMContentLoaded", this.step_func(function(e) {
    assert_true(e.isTrusted, "Should be trusted when first handled");
    event = e;
  }), true);

  window.onload = this.step_func_done(function() {
    var received = 0;
    var target = document.createElement("span");
    target.addEventListener("DOMContentLoaded", this.step_func(function(e) {
      assert_false(e.isTrusted, "Should not be trusted during redispatching");
      ++received;
    }), true);
    assert_true(event.isTrusted, "Should be trusted before redispatching");
    target.dispatchEvent(event);
    assert_false(event.isTrusted, "Should not be trusted after redispatching");
    assert_equals(received, 1);
  });
});
</script>