Include a "jsonrpc" property in all VM service responses.

runtime/vm/service/vmservice.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library vmservice;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 import 'dart:typed_data';
@@ skipping 138 matching lines @@
   static const _kStreamNotSubscribed = 104;
 
   var _errorMessages = {
     _kInvalidParams: 'Invalid params"',
     _kStreamAlreadySubscribed: 'Stream already subscribed',
     _kStreamNotSubscribed: 'Stream not subscribed',
   };
 
   String _encodeError(Message message, int code, {String details}) {
     var response = {
+      'jsonrpc': '2.0',
       'id' : message.serial,
       'error' : {
         'code': code,
         'message': _errorMessages[code],
       },
     };
     if (details != null) {
       response['error']['data'] = {
         'details': details,
       };
     }
     return JSON.encode(response);
   }
 
   String _encodeResult(Message message, Map result) {
     var response = {
+      'jsonrpc': '2.0',
       'id' : message.serial,
       'result' : result,
     };
     return JSON.encode(response);
   }
 
   bool _isAnyClientSubscribed(String streamId) {
     for (var client in clients) {
       if (client.streams.contains(streamId)) {
         return true;
@@ skipping 131 matching lines @@
   service.runningIsolates.isolateStartup(port_id, sp, name);
 }
 
 void _onStart() native "VMService_OnStart";
 
 void _onExit() native "VMService_OnExit";
 
 bool _vmListenStream(String streamId) native "VMService_ListenStream";
 
 void _vmCancelStream(String streamId) native "VMService_CancelStream";