chrome/browser/resources/tab_search/infinite_list.html

<style>
  :host {
    display: block;
    max-height: var(--list-max-height);
    overflow-x: hidden;
    overflow-y: auto;
    position: relative;
  }
</style>
<div id="items">
  <iron-selector id="selector" on-keydown="onKeyDown_"
      on-iron-items-changed="updateScrollerSize_"
      on-iron-select="onSelectedChanged_" role="listbox"
      selected-class="selected">
    <slot></slot>
  </iron-selector>
</div>