speculation-rules/prerender/resources/midi.https.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/speculation-rules/prerender/resources/utils.js"></script>
<script src="/speculation-rules/prerender/resources/deferred-promise-utils.js"></script>

<script>
const params = new URLSearchParams(location.search);

// The main test page (restriction-midi.https.html) loads the initiator page,
// then the initiator page will prerender itself with the `prerendering`
// parameter.
const isPrerendering = params.has('prerendering');

if (!isPrerendering) {
  loadInitiatorPage();
} else {
  const prerenderEventCollector = new PrerenderEventCollector();
  const promise = new Promise((resolve, reject) => {
    navigator.requestMIDIAccess({sysex: params.get("sysex") === "true"}).then(
      _ => { resolve(); },
      e => {
        // Chromium rejects the promise on trybots with an error like:
        // ALSA lib seq_hw.c:457:(snd_seq_hw_open) open /dev/snd/seq failed:
        //   Permission denied
        //
        // See https://crbug.com/371230 for a similar bug.
        //
        // Just ignore any errors for now. The test passes if the promise
        // settles after activation.
        resolve();
      });
  });
  prerenderEventCollector.start(promise, 'navigator.requestMIDIAccess');
}

</script>