third_party/web_platform_tests/webmessaging/message-channels/004.html

<!doctype html>
<title>cross-document channel</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<iframe src=004-1.html></iframe><iframe src=004-2.html></iframe>
<div id="log"></div>
<script>
var t = async_test();
onload = t.step_func(
  function() {
    var channel = new MessageChannel();
    window[0].postMessage(1, '*', [channel.port1]);
    window[1].postMessage(2, '*', [channel.port2]);
    channel = null;
    window.onmessage = t.step_func(
      function(e) {
        assert_equals(e.data, 1);
        t.done();
      });
  }
);
</script>