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chromium/third_party/blink/web_tests/external/wpt/webmessaging/with-options/message-channel-transferable.html 

<!doctype html>
<title>message channel as ports</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id=log></div>
<script>
async_test(function(t) {
  var channel = new MessageChannel();
  postMessage('', {targetOrigin: '*', transfer: [channel.port1, channel.port2]});
  onmessage = t.step_func(function(e) {
    assert_equals(e.ports.length, 2);
    t.done();
  });
}, "MessageChannel's ports as MessagePort objects");
</script>