third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/claim-shared-worker-fetch-worker.js

self.onconnect = (event) => {
  var port = event.ports[0];
  event.ports[0].onmessage = (evt) => {
    fetch(evt.data)
      .then(response => response.text())
      .then(text => port.postMessage(text));
  };
};