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chromium/third_party/blink/web_tests/fast/forms/color/color-picker-appearance-hue-slider-drag.html 

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

<input type='color'>

<script>
  window.onload = openPickerAppearanceOnly(document.querySelector('input'),() => {
    internals.pagePopupWindow.focus();
    const popupDocument = internals.pagePopupWindow.document;
    const hueSlider = popupDocument.querySelector('hue-slider');
    const hueSliderRect = hueSlider.getBoundingClientRect();
    eventSender.mouseMoveTo(hueSliderRect.left, hueSliderRect.top);
    eventSender.mouseDown();
    eventSender.mouseMoveTo(hueSliderRect.left + (hueSliderRect.width / 2), hueSliderRect.top);
    eventSender.mouseUp();
  });
</script>