Upstream service worker `fetch` tests to WPT

third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/resources/fetch-event-respond-with-argument-worker.js

 self.addEventListener('fetch', function(event) {
     var testcase = new URL(event.request.url).search;
     switch (testcase) {
     case '?response-object':
       event.respondWith(new Response('body'));
       break;
     case '?response-promise-object':
       event.respondWith(Promise.resolve(new Response('body')));
       break;
     case '?other-value':
       event.respondWith(new Object());
       break;
     }
   });