chromium/chrome/browser/resources/commerce/product_specifications/product_selection_menu.html

<style include="cr-shared-style cr-hidden-style">
  :host {
    --cr-url-list-item-padding: 0;
    --product-selector-width: 220px;
    text-align: start;
  }

  cr-action-menu {
    --cr-action-menu-padding: 0;
    --cr-menu-border-radius: 10px;
  }

  cr-expand-button {
    padding: 6px 16px;
  }

  hr {
    background: var(--color-product-specifications-divider);
    border: none;
    height: 1px;
    margin: 0;
  }

  .dropdown-item {
    padding: 0 16px;
  }

  .dropdown-spacer {
    height: 10px;
  }

  .expand-icon {
    padding: var(--iron-icon-padding);
  }

  .section-title {
    line-height: 16px;
    font-size: 12px;
    font-weight: 500;
  }

  #selectionContainer {
    box-sizing: border-box;
    overflow: clip;
    width: var(--product-selector-width);
  }

  #empty {
    font-weight: 500;
    line-height: 20px;
    padding: 12px;
    width: var(--product-selector-width);
  }

  #remove {
    --icon-size: 16px;
    --iron-icon-height: var(--icon-size);
    --iron-icon-width: var(--icon-size);
    color: var(--cr-secondary-text-color);
    font-weight: 400;
    font-size: 12px;
    gap: 8px;
    padding: 16px;
  }
</style>

<cr-lazy-render id="menu">
  <template>
    <cr-action-menu on-close="onClose_">
      <div id="selectionContainer">
        <template is="dom-repeat" items="[[sections]]" as="section">
          <cr-expand-button expanded="{{section.expanded}}" no-hover
              expand-icon="cr:arrow-drop-down"
              collapse-icon="cr:arrow-drop-up">
            <div class="section-title">[[section.title]]</div>
          </cr-expand-button>
          <cr-collapse opened="[[section.expanded]]">
            <template is="dom-repeat" items="[[section.entries]]">
              <cr-url-list-item class="dropdown-item" size="medium"
                  url="[[item.url]]" title="[[item.title]]"
                  data-url-section="[[section.sectionType]]"
                  description="[[getUrl_(item)]]" no-hover
                  on-click="onSelect_">
              </cr-url-list-item>
            </template>
            <!-- Add spacer instead of adding margin or padding to the -->
            <!-- parent for smooth expand/collapse transitions. -->
            <div class="dropdown-spacer"></div>
          </cr-collapse>
        </template>
        <div id="empty" hidden="[[sections]]">$i18n{emptyMenu}</div>
      </div>
      <template is="dom-if" if="[[selectedUrl.length]]">
        <hr>
        <button id="remove" class="dropdown-item" role="menuitem"
            on-click="onRemoveClick_">
          <cr-icon icon="product-specifications:remove"></cr-icon>
          $i18n{removeColumn}
        </button>
      </template>
    </cr-action-menu>
  </template>
</cr-lazy-render>