Fix analyzer warnings in dart:_vmservice

sdk/lib/vmservice/message.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.
 
-part of vmservice;
+part of dart._vmservice;
 
 class Message {
   final Completer _completer = new Completer.sync();
   bool get completed => _completer.isCompleted;
   /// Future of response.
   Future<String> get response => _completer.future;
   Client client;
 
   // Client-side identifier for this message.
   final serial;
@@ skipping 124 matching lines @@
   }
 
   void setErrorResponse(int code, String details) {
     _completer.complete(encodeRpcError(this, code,
                                        details: '$method: $details'));
   }
 }
 
 external bool sendIsolateServiceMessage(SendPort sp, List m);
 external void sendRootServiceMessage(List m);