Remove an obsolete error from the spec and an obsolete command-line flag

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.
 
 library domain.completion;
 
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
@@ skipping 121 matching lines @@
     }
     //
     // Return the result.
     //
     return new CompletionResult(
         request.replacementOffset, request.replacementLength, suggestions);
   }
 
   @override
   Response handleRequest(Request request) {
-    if (server.searchEngine == null) {
-      return new Response.noIndexGenerated(request);
-    }
     return runZoned(() {
       String requestName = request.method;
       if (requestName == COMPLETION_GET_SUGGESTIONS) {
         processRequest(request);
         return Response.DELAYED_RESPONSE;
       }
       return null;
     }, onError: (exception, stackTrace) {
       server.sendServerErrorNotification(
           'Failed to handle completion domain request: ${request.toJson()}',
@@ skipping 173 matching lines @@
   final int replacementOffset;
 
   /**
    * The suggested completions.
    */
   final List<CompletionSuggestion> suggestions;
 
   CompletionResult(
       this.replacementOffset, this.replacementLength, this.suggestions);
 }