Consistently use implements when one interface inherits from another interface

pkg/analysis_server/lib/plugin/protocol/protocol.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.
 
 /**
  * Support for client code that needs to interact with the requests, responses
  * and notifications that are part of the analysis server's wire protocol.
  */
 library analysis_server.plugin.protocol.protocol;
 
 import 'dart:collection';
 import 'dart:convert' hide JsonDecoder;
 
 import 'package:analysis_server/src/protocol/protocol_internal.dart';
 
 part 'generated_protocol.dart';
 
 /**
  * A [RequestHandler] that supports [startup] and [shutdown] methods.
  *
  * Clients may not extend, implement or mix-in this class.
  */
-abstract class DomainHandler extends RequestHandler {
+abstract class DomainHandler implements RequestHandler {
   /**
    * Perform any operations associated with the shutdown of the domain. It is
    * not guaranteed that this method will be called. If it is, it will be
    * called after the last [Request] has been made.
    */
   void shutdown() {}
 
   /**
    * Perform any operations associated with the startup of the domain. This
    * will be called before the first [Request].
@@ skipping 522 matching lines @@
     jsonObject[ID] = id;
     if (error != null) {
       jsonObject[ERROR] = error.toJson();
     }
     if (_result != null) {
       jsonObject[RESULT] = _result;
     }
     return jsonObject;
   }
 }