Add the streamListen and streamCancel rpcs to the vm service.

runtime/observatory/tests/service/echo_test.dart

Index: runtime/observatory/tests/service/echo_test.dart
diff --git a/runtime/observatory/tests/service/echo_test.dart b/runtime/observatory/tests/service/echo_test.dart
index 8d31f2fd65872fbca88d7ee2df5f8a64a8cf6122..4ae020c3952938ea275e14b403acdd87fe8f973b 100644
--- a/runtime/observatory/tests/service/echo_test.dart
+++ b/runtime/observatory/tests/service/echo_test.dart
@@ -24,7 +24,7 @@ var tests = [
 
 (Isolate isolate) {
   Completer completer = new Completer();
-  isolate.vm.events.stream.listen((ServiceEvent event) {
+  isolate.vm.getEventStream('_Echo').listen((ServiceEvent event) {
     if (event.eventType == '_Echo') {
       expect(event.data.lengthInBytes, equals(3));
       expect(event.data.getUint8(0), equals(0));