both localized strings and
 * any data that is important to have ready from a very early stage (e.g. things
 * that must be displayed right away).
 *
 * Note that loadTimeData is not guaranteed to be consistent between page
 * refreshes (https://crbug.com/740629) and should not contain values that might
 * change if the page is re-opened later.
 */

    // #import {assert} from './assert.m.js';
    // #import {parseHtmlSubset} from './parse_html_subset.m.js';

    /**
 * @typedef {{
 *   substitutions: (!Ar