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chromium/third_party/blink/web_tests/fast/forms/color-scheme/suggestion-picker/datetimelocal-suggestion-picker-appearance.html 

<!DOCTYPE html>
<meta name=fuzzy content="maxDifference=0-3; totalPixels=0-1000">
<meta name="color-scheme" content="light dark">
<script src="../../../../resources/testdriver.js"></script>
<script src="../../../../resources/testdriver-vendor.js"></script>
<script src="../../resources/picker-common.js"></script>

<body style="background-color: #eeffff;">
<input type=datetime-local value="10000-12-31T23:59" list="suggestions" style="width: 300px;" step="0.001">
<datalist id=suggestions>
  <option>2012-11-31T00:00</option> <!--invalid-->
  <option>2012-11-31</option> <!--invalid-->
  <option>foo</option> <!--invalid-->
  <option label="Today">2012-11-22T12:00</option>
  <option label="Tomorrow">2012-11-23T12:00</option>
  <option>2012-11-22T01:23</option>
  <option>2012-11-22T01:23:45</option>
  <option>2012-11-22T01:23:45.678</option>
  <option>2012-11-22T01:06</option>
  <option>2012-11-22T01:07</option>
  <option>2012-11-22T01:08</option>
  <option>2012-11-22T01:09</option>
  <option>2012-11-22T01:10</option>
  <option>2012-11-22T01:11</option>
</datalist>

<script>
  window.onload = openPickerAppearanceOnly(document.querySelector('input'),() => {
    internals.pagePopupWindow.focus();
    eventSender.keyDown('ArrowDown');
  });
</script>