 {
      // Treat the first `metadatachange` message as a hint that the iframe is
      // done loading. This event is sent in response to `DOMContentLoaded` within the
      // ViaHTML iframe, so sub-resources on the page may still be loading.
      loadingIndicator.classList.add('is-done');

      const metadata = message.metadata;
      document.title = `Via: ${metadata.title}`;

      // Sync top frame URL with the URL being proxied inside the iframe.
      // This may be different than the originally r