Support JSON-RPC 2.0-compatible VM service events.

runtime/vm/service.cc

Index: runtime/vm/service.cc
diff --git a/runtime/vm/service.cc b/runtime/vm/service.cc
index 4674f143e656d646e288ec0981b222196f61291e..71924896a7e7400b304c734829868900a18d9add 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -681,8 +681,11 @@ void Service::HandleEvent(ServiceEvent* event) {
   ASSERT(stream_id != NULL);
   {
     JSONObject jsobj(&js);
-    jsobj.AddProperty("event", event);
-    jsobj.AddProperty("streamId", stream_id);
+    jsobj.AddProperty("jsonrpc", "2.0");
+    jsobj.AddProperty("method", "streamNotify");
+    JSONObject params(&jsobj, "params");
+    params.AddProperty("streamId", stream_id);
+    params.AddProperty("event", event);
   }
   PostEvent(stream_id, event->KindAsCString(), &js);
 }