Basic tests for sending messages over a navigator.connect initiated channel.

LayoutTests/http/tests/navigatorconnect/resources/echo-worker.js

+var client;
+self.addEventListener('crossoriginconnect', function(event) {
+  client = event.client;
+  event.acceptConnection(true);
+});
+
+
+self.addEventListener('crossoriginmessage', function(event) {
+  client.postMessage(event.data, event.ports);
+});