chromium/chrome/browser/resources/chromeos/emoji_picker/emoji_group_button.html

<style>
  :host {
    display: flex;
    height: calc(var(--emoji-size) + 2 * var(--emoji-picker-group-button-padding));
    justify-content: center;
    scroll-snap-align: none;
    width: var(--emoji-size);
  }

  #group-button {
    --cr-icon-button-size: var(--emoji-size);
    --cr-icon-button-icon-size: var(--emoji-picker-group-button-icon-size, 20px);
    font-size: 20px;
    margin: 0;
    padding-left: 0;
    padding-right: 0;
    padding-top: var(--emoji-picker-group-button-padding, 0px);
    padding-bottom: var(--emoji-picker-group-button-padding, 0px);
    border-radius: var(--emoji-picker-group-button-border-radius, 0px);
  }

  #group-button:not(.emoji-group-active) {
    --cr-icon-button-fill-color: var(--emoji-picker-tab-unselected-color);
  }

  #group-button.emoji-group-active {
    --cr-icon-button-fill-color: var(--emoji-picker-tab-selected-color);
  }

  cr-icon-button {
    --cr-icon-button-focus-outline-color: var(--emoji-picker-focus-ring-color);
  }
</style>

<cr-icon-button
    id="group-button"
    iron-icon="[[icon]]"
    class$="[[calculateClassName(active)]]"
    on-click="handleClick"
    aria-label="[[name]]"
    aria-pressed$="[[getAriaPressedState(active)]]"
    disabled="[[disabled]]"
    custom-tab-index="[[customTabIndex]]">
</cr-icon-button>