static getWarningsForFontUrls(warningUrls) {
    /** @type {Map<string, number>} */
    const warningCountByOrigin = new Map();
    for (const warningUrl of warningUrls) {
      const origin = UrlUtils.getOrigin(warningUrl);
      if (!origin) continue;

      const count = warningCountByOrigin.get(origin) || 0;
      warningCountByOrigin.set(origin, count + 1);
    }

    const warnings = [...warningCountByOrigin].map(([fontOrigin, fontCountForOrigin]) => {
      return str_(UIStrings.undeclaredFontOriginWarning, {fontCountForOrigin, fontOrigin});
    });
    return warnings;
  }
Some pages load many fonts we can't check, so dedupe on origin.
@param {Array<string>} warningUrls
@return {Array<LH.IcuMessage>}