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chromium/third_party/blink/web_tests/external/wpt/quirks/html-fills-viewport-quirk-ref.html 

<!DOCTYPE html>
<body style="width: 100vw; height: 100vh; margin: 0; padding: 10px 11px 12px 14px; box-sizing: border-box">
  <div id="border" style="border: solid; width: 100%; height: 100%; box-sizing: border-box">
    <div style="width: 100px; height: 100px; background: green"></div>
  </div>
</body>