Import w3c tests for the service workers

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

 var port;
 
 // Exercise the 'onmessage' handler:
 self.onmessage = function(e) {
   var message = e.data;
   if ('port' in message) {
     port = message.port;
   }
 };
 
 // And an event listener:
 self.addEventListener('message', function(e) {
     var message = e.data;
     if ('value' in message) {
       port.postMessage('Acking value: ' + message.value);
     } else if ('done' in message) {
       port.postMessage('quit');
     }
   });