chromium/third_party/blink/web_tests/external/wpt/streams/transferable/window.html

<!DOCTYPE html>
<meta charset="utf-8">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/helpers.js"></script>
<script>
'use strict';

promise_test(t => {
  const orig = createOriginalReadableStream();
  const promise = testMessageEvent(window);
  postMessage(orig, '*', [orig]);
  assert_true(orig.locked, 'the original stream should be locked');
  return promise;
}, 'window.postMessage should be able to transfer a ReadableStream');

promise_test(t => {
  const orig = createOriginalReadableStream();
  const mc = new MessageChannel();
  const promise = testMessageEvent(mc.port1);
  mc.port1.start();

  mc.port2.postMessage(orig, [orig]);
  mc.port2.close();
  assert_true(orig.locked, 'the original stream should be locked');
  return promise;
}, 'port.postMessage should be able to transfer a ReadableStream');

promise_test(t => {
  const orig = createOriginalReadableStream();
  const promise = new Promise(resolve => {
    addEventListener('message', t.step_func(evt => {
      const [rs1, rs2] = evt.data;
      assert_equals(rs1, rs2, 'both ReadableStreams should be the same object');
      resolve();
    }), {once: true});
  });
  postMessage([orig, orig], '*', [orig]);
  return promise;
}, 'the same ReadableStream posted multiple times should arrive together');

const onloadPromise = new Promise(resolve => onload = resolve);

promise_test(() => {
  const orig = createOriginalReadableStream();
  const promise = testMessageEvent(window);
  return onloadPromise.then(() => {
    const echoIframe = document.querySelector('#echo');
    echoIframe.contentWindow.postMessage(orig, '*', [orig]);
    return promise;
  });
}, 'transfer to and from an iframe should work');
</script>

<iframe id=echo src="resources/echo-iframe.html" style="display:none"></iframe>