Add the streamListen and streamCancel rpcs to the vm service.

runtime/observatory/lib/service_common.dart

Index: runtime/observatory/lib/service_common.dart
diff --git a/runtime/observatory/lib/service_common.dart b/runtime/observatory/lib/service_common.dart
index 50774c42c1bd2053056001d0872f59c13bf3c118..58d69cfc82bd0074445fbe24ca7925b0c9519ec1 100644
--- a/runtime/observatory/lib/service_common.dart
+++ b/runtime/observatory/lib/service_common.dart
@@ -210,7 +210,8 @@ abstract class CommonWebSocketVM extends VM {
         return;
       }
       var event = map['event'];
-      postServiceEvent(event, data);
+      var streamId = map['streamId'];
+      postServiceEvent(streamId, event, data);
     });
   }
 
@@ -221,7 +222,8 @@ abstract class CommonWebSocketVM extends VM {
     }
     var event = map['event'];
     if (event != null) {
-      postServiceEvent(event, null);
+      var streamId = map['streamId'];
+      postServiceEvent(streamId, event, null);
       return;
     }