Unify the server and plugin versions of the generators

pkg/analysis_server/lib/plugin/edit/assist/assist_core.dart

 // Copyright (c) 2015, 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 analysis_server.plugin.edit.assist.assist_core;
 
 import 'dart:async';
 
-import 'package:analysis_server/plugin/protocol/protocol.dart'
+import 'package:analysis_server/protocol/protocol_generated.dart'
     show SourceChange;
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * A description of a single proposed assist.
  *
  * Clients may not extend, implement or mix-in this class.
  */
 class Assist {
@@ skipping 96 matching lines @@
 
   /**
    * Initialize a newly created kind of assist to have the given [name],
    * [relevance] and [message].
    */
   const AssistKind(this.name, this.relevance, this.message);
 
   @override
   String toString() => name;
 }