When no service response is requested, send null back to the service isolate so it can cleanup

runtime/vm/json_stream.h

 // 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.
 
 #ifndef VM_JSON_STREAM_H_
 #define VM_JSON_STREAM_H_
 
 #include "include/dart_api.h"  // for Dart_Port
 #include "platform/json.h"
 #include "vm/allocation.h"
@@ skipping 90 matching lines @@
   // Returns true if there is an param with key and value, false
   // otherwise.
   bool ParamIs(const char* key, const char* value) const;
 
   const char* method() const { return method_; }
   const char** param_keys() const { return param_keys_; }
   const char** param_values() const { return param_values_; }
 
  private:
   void Clear();
+  void PostNullReply(Dart_Port port);
 
   void OpenObject(const char* property_name = NULL);
   void CloseObject();
 
   void OpenArray(const char* property_name = NULL);
   void CloseArray();
 
   void PrintValueBool(bool b);
   void PrintValue(intptr_t i);
   void PrintValue64(int64_t i);
@@ skipping 203 matching lines @@
 
   friend class JSONObject;
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(JSONArray);
 };
 
 }  // namespace dart
 
 #endif  // VM_JSON_STREAM_H_