chromium/third_party/blink/web_tests/fast/speechsynthesis/speech-synthesis-voices-changed.html

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<script src="../../resources/js-test.js"></script>
</head>
<body>

<div id="console"></div>

<script>
    if (window.internals)
        internals.enableMockSpeechSynthesizer(window);

    if (window.testRunner)
        testRunner.waitUntilDone();

    window.jsTestIsAsync = true;

    var list = speechSynthesis.getVoices();
    debug('Initially, there are ' + list.length + ' voices.');

    speechSynthesis.onvoiceschanged = function() {
        debug('Got onvoiceschanged event.');

        list = speechSynthesis.getVoices();
        debug('Now there are ' + list.length + ' voices.');

        finishJSTest();
    }

</script>

</body>
</html>