Import w3c tests for the service workers

third_party/WebKit/LayoutTests/imported/wpt/service-workers/service-worker/resources/shared-worker-controlled.js

 onconnect = function(e) {
   var port = e.ports[0];
   var xhr = new XMLHttpRequest();
   xhr.onload = function() { port.postMessage(this.responseText); };
   xhr.onerror = function(e) { port.postMessage(e); };
   xhr.open('GET', 'dummy.txt?simple', true);
   xhr.send();
 };