LayoutTests/http/tests/workers/service/resources/basic-activate-event-worker.js

let resolvedExtendLifetimePromise = false;

self.addEventListener("install", (event) => {
    self.addEventListener("activate", (event) => {
        event.waitUntil(new Promise((resolve, reject) => {
            setTimeout(() => {
                resolvedExtendLifetimePromise = true;
                resolve();
            }, 50);
        }));
    });
});

self.addEventListener("message", (event) => {
    event.source.postMessage(resolvedExtendLifetimePromise);
});