chromium/third_party/blink/web_tests/external/wpt/service-workers/service-worker/multi-globals/incumbent/incumbent.https.html

<!DOCTYPE html>
<title>Incumbent page used as a test helper</title>

<iframe src="../current/current.https.html" id="c"></iframe>
<iframe src="../relevant/relevant.https.html" id="r"></iframe>

<script>
'use strict';

const current = document.querySelector('#c').contentWindow;
const relevant = document.querySelector('#r').contentWindow;

window.testRegister = options => {
    return current.navigator.serviceWorker.register.call(relevant.navigator.serviceWorker, 'test-sw.js', options);
};

window.testGetRegistration = () => {
    return current.navigator.serviceWorker.getRegistration.call(relevant.navigator.serviceWorker, 'test-sw.js');
};
</script>