Generate constants in server as we do in plugin

pkg/analysis_server/lib/src/domain_completion.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.
 
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
+import 'package:analysis_server/protocol/protocol_constants.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/collections.dart';
-import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_abstract.dart';
 import 'package:analysis_server/src/plugin/plugin_manager.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
 import 'package:analysis_server/src/services/completion/completion_core.dart';
 import 'package:analysis_server/src/services/completion/completion_performance.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart' as plugin;
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:analyzer_plugin/protocol/protocol_constants.dart' as plugin;
@@ skipping 119 matching lines @@
     // Return the result.
     //
     return new CompletionResult(
         request.replacementOffset, request.replacementLength, suggestions);
   }
 
   @override
   Response handleRequest(Request request) {
     return runZoned(() {
       String requestName = request.method;
-      if (requestName == COMPLETION_GET_SUGGESTIONS) {
+      if (requestName == COMPLETION_REQUEST_GET_SUGGESTIONS) {
         processRequest(request);
         return Response.DELAYED_RESPONSE;
       }
       return null;
     }, onError: (exception, stackTrace) {
       server.sendServerErrorNotification(
           'Failed to handle completion domain request: ${request.toJson()}',
           exception,
           stackTrace);
     });
@@ skipping 131 matching lines @@
   final int replacementOffset;
 
   /**
    * The suggested completions.
    */
   final List<CompletionSuggestion> suggestions;
 
   CompletionResult(
       this.replacementOffset, this.replacementLength, this.suggestions);
 }