gecko/browser/base/content/aboutTabCrashed.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

function parseQueryString() {
  let url = document.documentURI;
  let queryString = url.replace(/^about:tabcrashed?e=tabcrashed/, "");

  let titleMatch = queryString.match(/d=([^&]*)/);
  return titleMatch && titleMatch[1] ? decodeURIComponent(titleMatch[1]) : "";
}

document.title = parseQueryString();