Dart: Refactor Stubs

mojo/dart/apptests/test_apps/echo/lib/main.dart

Index: mojo/dart/apptests/test_apps/echo/lib/main.dart
diff --git a/mojo/dart/apptests/test_apps/echo/lib/main.dart b/mojo/dart/apptests/test_apps/echo/lib/main.dart
index 76ad19668b33036fc92569476b3dba9bc56dcd9a..9f8cb8d6a32e391647ab86ae341a7cf082cb02bc 100644
--- a/mojo/dart/apptests/test_apps/echo/lib/main.dart
+++ b/mojo/dart/apptests/test_apps/echo/lib/main.dart
@@ -45,7 +45,7 @@ class EchoServiceImpl implements EchoService {
     // It is not allowed to do an unbind in the midst of handling an event, so
     // it is delayed until popping back out to the event loop.
     Timer.run(() {
-      final endpoint = stub.unbind();
+      final endpoint = stub.ctrl.unbind();
       new EchoServiceImpl(app, endpoint);
     });
   }