y, although
       * the loading bar will still briefly fade in and out.
       */
      function showLoadingIndicator() {
        const loadingIndicator = document.querySelector('.js-loading-indicator');
        setTimeout(() => loadingIndicator.classList.add('is-loading'), 500);
      }

      /**
       * Copy the fragment from the top frame's URL to the iframe's URL.
       *
       * This is needed so that direct links to annotations, which use a
       * `#annotations:` fragment, are respected by the 