chromium/chrome/browser/resources/print_preview/ui/duplex_settings.html

<style include="print-preview-shared cr-hidden-style md-select">
  :host {
    --duplex-icon-side-padding: 8px;
    --duplex-icon-size: 16px;
  }

  .md-select {
    background-position: var(--duplex-icon-side-padding) center,
        calc(100% - var(--md-select-side-padding)) center;
    background-size: var(--duplex-icon-size), var(--md-arrow-width);
    padding-inline-start: 32px;
  }

  :host-context([dir=rtl]) .md-select {
    background-position-x: calc(100% - var(--duplex-icon-side-padding)),
        var(--md-select-side-padding);
  }
</style>
<print-preview-settings-section hidden$="[[!settings.duplex.available]]">
  <div slot="title">
    <label id="label">$i18n{optionTwoSided}</label>
  </div>
  <div slot="controls" class="checkbox">
    <cr-checkbox id="duplex" aria-labelledby="label"
        disabled$="[[getDisabled_(settings.duplex.setByPolicy, disabled)]]"
        on-change="onCheckboxChange_">
      $i18n{printOnBothSidesLabel}
    </cr-checkbox>
  </div>
</print-preview-settings-section>
<cr-collapse opened="[[getOpenCollapse_(
    settings.duplex.*, settings.duplexShortEdge.available)]]">
  <print-preview-settings-section>
    <div slot="title"></div>
    <div slot="controls">
      <select class="md-select" aria-labelledby="duplex"
          style="background-image: [[getBackgroundImages_(
            settings.duplexShortEdge.value, dark)]];"
          disabled$="[[getDisabled_(
            settings.duplexShortEdge.setByPolicy, disabled)]]"
          value="{{selectedValue::change}}">
        <option value="[[duplexValueEnum_.LONG_EDGE]]">
          $i18n{optionLongEdge}
        </option>
        <option value="[[duplexValueEnum_.SHORT_EDGE]]">
          $i18n{optionShortEdge}
        </option>
      </select>
    </div>
  </print-preview-settings-section>
</cr-collapse>