chromium/third_party/blink/web_tests/fast/forms/select/select-autofilled.html

<!DOCTYPE html>
<body>
<style>
    select {
        width: 168px;
        padding: 5px;
        font-size: 16px;
        height: 34px;
        background: transparent;
    }
</style>
<p>The background should be blue.</p>
    <select id = "select">
        <option>CA</option>
        <option>TX</option>
    </select>
<script>
    var select = document.getElementById('select');
    if (window.internals)
        internals.setAutofilled(select, true);
</script>
</body>