Reorganize VM Service client

runtime/bin/vmservice/client/lib/src/observatory/request_manager.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 observatory;
 
 /// A request response interceptor is called for each response.
 typedef void RequestResponseInterceptor();
 
 abstract class RequestManager extends Object with ChangeNotifierMixin {
@@ skipping 44 matching lines @@
   /// future which contains the reply from the VM service.
   Future<String> request(String requestString);
 }
 
 
 class HttpRequestManager extends RequestManager {
   Future<String> request(String requestString) {
     return HttpRequest.getString(prefix + requestString);
   }
 }