Revert "Change some platform libraries to use `part of URI`."

sdk/lib/vmservice/client.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 "dart:_vmservice";
+part of dart._vmservice;
 
 // A service client.
 abstract class Client {
   final VMService service;
   final bool sendEvents;
   final Set<String> streams = new Set<String>();
 
   Client(this.service, {bool sendEvents: true}) : this.sendEvents = sendEvents {
     service._addClient(this);
   }
@@ skipping 20 matching lines @@
     }
   }
 
   // Sends a result to the client.  Implemented in subclasses.
   void post(dynamic result);
 
   dynamic toJson() {
     return {};
   }
 }