         // Wait for registration to finish before dropping the <script> tag.
            // Otherwise, the browser will load the script multiple times,
            // potentially different versions.
            var serviceWorkerUrl =
                "flutter_service_worker.js?v=" + serviceWorkerVersion;
            navigator.serviceWorker.register(serviceWorkerUrl).then((reg) => {
                function waitForActivation(serviceWorker) {
                    serviceWorker.addEventListener("statechange", (