LayoutTests/fast/css/content-glyph-computed-style.html

<!DOCTYPE html>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>

<style>
select, ::picker(select) {
    appearance: base-select;
}
</style>
<select id="baseSelect">
  <option>option</option>
</select>
<select id="menulistSelect" style="appearance: auto">
  <option>option</option>
</select>

<script>
  test(function() {
    assert_equals(getComputedStyle(baseSelect, '::picker-icon').content, 'picker-down / ""');
  }, 'The user agent stylesheet gives select::picker-icon a glyph keyword, which computes to itself.');

  test(function() {
    assert_equals(getComputedStyle(menulistSelect, '::picker-icon').content, 'picker-down / ""');
  }, 'select::picker-icon computes the same regardless of the used appearance.');

  test(function() {
    baseSelect.style.setProperty('content', 'picker-up');
    assert_equals(baseSelect.style.getPropertyValue('content'), '');
    baseSelect.style.removeProperty('content');
  }, 'A glyph keyword cannot be set through CSSOM either.');
</script>