chromium/third_party/blink/web_tests/external/wpt/service-workers/service-worker/resources/fetch-request-xhr-sync-worker.js

'use strict';

self.onfetch = function(event) {
  if (event.request.url.indexOf('non-existent-file.txt') !== -1) {
    event.respondWith(new Response('Response from service worker'));
  }
};