chromium/ash/webui/firmware_update_ui/resources/firmware_update_app.html

<style include="firmware-shared-fonts firmware-shared">
  .header-container {
    align-items: flex-end;
    display: flex;
    height: 68px;
    margin-bottom: 24px;
  }
</style>
<div id="container" class="firmware-default-font">
  <div class="header-container">
    <h1 id="header" class="firmware-header-font">
      [[i18n('appTitle')]]
    </h1>
  </div>
  <peripheral-updates-list></peripheral-updates-list>
  <firmware-update-dialog></firmware-update-dialog>
  <firmware-confirmation-dialog></firmware-confirmation-dialog>
</div>