_loadFromGistURL(urlStr) {
    try {
      const url = new URL(urlStr);

      if (url.origin !== 'https://gist.github.com') {
        logger.error('URL was not a gist');
        return;
      }

      const match = url.pathname.match(/[a-f0-9]{5,}/);
      if (match) {
        history.pushState({}, '', `${LighthouseReportViewer.APP_URL}?gist=${match[0]}`);
        this._loadFromDeepLink();
      }
    } catch (err) {
      logger.error('Invalid URL');
    }
  }
Loads report json from gist URL, if valid. Updates page URL with gist ID
and loads from github.
@param {string} urlStr Gist URL.
@private