navigation-start-post-before-unload.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /hr-time/navigation-start-post-before-unload.html - WPT Dashboard Interop Dashboard

<!doctype html>

<html>

<head>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

</head>

<body>

<script>

    function busyWait(millis) {

        const start = performance.now();

        while (performance.now() < start + millis) {}

    promise_test(async t => {

        const delay = 3000;

        const iframe = document.createElement('iframe');

        iframe.src = './resources/now_frame.html';

        document.body.appendChild(iframe);

        await new Promise(resolve => iframe.addEventListener('load', resolve));

        iframe.contentWindow.addEventListener('beforeunload', () => {

            busyWait(delay);

});

        iframe.src = './resources/post.html';

        await new Promise(resolve => this.addEventListener('message', ({data}) => {

            if (data === 'done')

                resolve();

        }));

        const entry = iframe.contentWindow.performance.getEntriesByType('navigation')[0];

        assert_less_than(entry.fetchStart, delay);

    }, 'timeOrigin should be set after beforeunload');

</script>

</body>

</html>