implement ByteStreamClientChannel close

pkg/analysis_server/lib/src/channel.dart

 // Copyright (c) 2014, 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.
 
 library channel;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 184 matching lines @@
         .transform(new ResponseConverter())
         .asBroadcastStream();
     notificationStream = jsonStream
         .where((json) => json[Notification.EVENT] != null)
         .transform(new NotificationConverter())
         .asBroadcastStream();
   }
 
   @override
   Future close() {
-    // TODO: implement close
+    return output.close();
   }
 
   @override
   Future<Response> sendRequest(Request request) {
     String id = request.id;
     output.writeln(JSON.encode(request.toJson()));
     return responseStream.firstWhere((Response response) => response.id == id);
   }
 }
 
@@ skipping 130 matching lines @@
       }
     }
   }
 
   @override
   void close() {
     closed = true;
     sink.close();
   }
 }