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chromium/third_party/blink/web_tests/external/wpt/css/css-ui/compute-kind-widget-fallback-select-menulist-button-ref.html 

<!DOCTYPE html>
<meta charset="utf-8">
<title>Reference: Compute kind of widget - fallback - select-menulist-button</title>
<style>
    #container { width: 500px; }
    #select-menulist-button { appearance: none; appearance: menulist-button; }
</style>
<div id="container">
    <select id="select-menulist-button"><option>select-menulist-button</option></select>
</div>