service-workers/service-worker/resources/dummy-shared-worker-interceptor.js

var worker_text = 'onconnect = function(e) { e.ports[0].postMessage("worker loading intercepted by service worker"); };';

self.onfetch = function(event) {
  if (event.request.url.indexOf('dummy-shared-worker.js') != -1) {
    event.respondWith(new Response(
        worker_text, {headers: {"Content-Type": "application/javascript"}}));
  }
};