html/semantics/forms/the-select-element/stylable-select/resources/stylable-select-styles.css

/* These are UA styles for select and stylable select. */

.stylable-select-container {
  box-sizing: border-box;
  display: inline-block;
}

.stylable-select-datalist {
  box-shadow: 0px 12.8px 28.8px rgba(0, 0, 0, 0.13), 0px 0px 9.2px rgba(0, 0, 0, 0.11);
  box-sizing: border-box;
  overflow: auto;
  border: 1px solid rgba(0, 0, 0, 0.15);
  border-radius: 0.25em;
  padding-block: 0.25em;
  padding-inline: 0;
  background-color: Field;
  margin: 0;
  inset: auto;
  min-inline-size: anchor-size(self-inline);
  min-block-size: 1lh;
  inset-block-start: anchor(self-end);
  inset-inline-start: anchor(self-start);

  font-family: Arial;
  font-size: 13.3333px;
}

/* These are the UA styles for <option> in chromium.
 * They will either have to be specced or also added to the main test file.
 * TODO(crbug.com/1511354): Spec these UA styles. */
.stylable-select-option {
  min-height: 1.2em;
  padding: 0px 2px 1px;
  white-space: nowrap;
}

.stylable-select-button {
  color: FieldText;
  background-color: Field;
  appearance: none;
  padding: 0.25em;
  border: 1px solid ButtonBorder;
  cursor: default;
  text-align: inherit;
  display: inline-flex;
  flex-grow: 1;
  flex-shrink: 1;
  align-items: center;
  overflow-x: hidden;
  overflow-y: hidden;
}

.stylable-select-button-icon {
  background-image: url(data:image/svg+xml,%3Csvg%20width%3D%2220%22%20height%3D%2214%22%20viewBox%3D%220%200%2020%2016%22%20fill%3D%22none%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3E%3Cpath%20d%3D%22M4%206%20L10%2012%20L%2016%206%22%20stroke%3D%22WindowText%22%20stroke-width%3D%223%22%20stroke-linejoin%3D%22round%22%2F%3E%3C%2Fsvg%3E);
  background-origin: content-box;
  background-repeat: no-repeat;
  background-size: contain;
  opacity: 1;
  outline: none;
  margin-inline-start: 0.25em;
  padding-block: 2px;
  padding-inline: 3px;
  block-size: 1.0em;
  inline-size: 1.2em;
  min-inline-size: 1.2em;
  max-inline-size: 1.2em;
  display: block;
}

.stylable-select-selectedoption {
  color: inherit;
  min-inline-size: 0px;
  max-block-size: 100%;
  flex-grow: 1;
  flex-shrink: 1;
  overflow: hidden;
  display: inline;
}