Allow root level requests in the vm service.

runtime/vm/service.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_SERVICE_H_
 #define VM_SERVICE_H_
 
 #include "include/dart_api.h"
 
 #include "vm/allocation.h"
 
 namespace dart {
 
 class Instance;
 class Isolate;
+class RawInstance;
 
 class Service : public AllStatic {
  public:
-  static void HandleServiceMessage(Isolate* isolate, const Instance& message);
+  // Handles a message which is not directed to an isolate.
+  static void HandleRootMessage(const Instance& message);
+
+  // Handles a message which is directed to a particular isolate.
+  static void HandleIsolateMessage(Isolate* isolate, const Instance& message);
 };
 
 }  // namespace dart
 
 #endif  // VM_SERVICE_H_