chromium/ash/webui/common/resources/cr_elements/cr_toast/cr_toast_manager.html

<style include="cr-hidden-style">
  #content {
    display: flex;
    flex: 1;
  }

  .collapsible {
    overflow: hidden;
    text-overflow: ellipsis;
  }

  span {
    white-space: pre;
  }

  .elided-text {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }
</style>
<cr-toast id="toast" duration="[[duration]]">
  <div id="content" class="elided-text"></div>
  <slot id="slotted"></slot>
</cr-toast>