Update navigator.services API to use the new services.onconnect event [1/3].

LayoutTests/http/tests/navigatorconnect/resources/test-helpers.js

 // Helper method that waits for a {success: <boolean>, result: any} reply on
 // a port and returns a promise that resolves (if success is true) or rejects
 // the promise with the value of the result attribute.
 function reply_as_promise(t, port) {
   return new Promise(function(resolve, reject) {
       var got_reply = false;
       port.onmessage = t.step_func(function(event) {
         assert_false(got_reply);
         assert_true('success' in event.data);
         assert_true('result' in event.data);
@@ skipping 68 matching lines @@
       navigator.services.onmessage = function(event) {
         channel.port2.postMessage(event.data, event.ports);
       };
       channel.port1.targetURL = port.targetURL;
       channel.port1.name = port.name;
       channel.port1.data = port.data;
       return channel.port1;
     }
   );
 }
+