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

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

Index: LayoutTests/http/tests/navigatorconnect/resources/echo-worker.js
diff --git a/LayoutTests/http/tests/navigatorconnect/resources/echo-worker.js b/LayoutTests/http/tests/navigatorconnect/resources/echo-worker.js
new file mode 100644
index 0000000000000000000000000000000000000000..37d12869b9c57593d716e20ac6a0a7ebe26e89fa
--- /dev/null
+++ b/LayoutTests/http/tests/navigatorconnect/resources/echo-worker.js
@@ -0,0 +1,10 @@
+var client;
+self.addEventListener('crossoriginconnect', function(event) {
+  client = event.client;
+  event.acceptConnection(true);
+});
+
+
+self.addEventListener('crossoriginmessage', function(event) {
+  client.postMessage(event.data, event.ports);
+});