chromium/content/test/data/workers/service_worker.js

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

self.addEventListener('fetch', event => {
  if (event.request.url.indexOf('?intercept') != -1) {
    event.respondWith(fetch(event.request));
  }
});