chromium/ash/webui/common/resources/cellular_setup/activation_verification_page.html

<style>
  #pageBody {
    height: 282px;
    margin-top: -20px;
    overflow: hidden;
  }

  #animationContainer {
    display: flex;
    height: 216px;
    margin-bottom: 30px;
    margin-top: 24px;
  }

  cros-lottie-renderer {
    margin: auto;
  }
</style>

<base-page>
  <div slot="page-body" id="pageBody" class="layout vertical center-center">
    <span>[[i18n('verifyingActivationCode')]]</span>
    <div id="animationContainer">
      <cros-lottie-renderer id="spinner"
          asset-url="chrome://resources/ash/common/cellular_setup/spinner.json"
          autoplay dynamic aria-hidden>
      </cros-lottie-renderer>
    </div>
  </div>
</base-page>