Extract DocumentationCommentToken with field.

pkg/analyzer/lib/src/generated/incremental_resolver.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 engine.incremental_resolver;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/src/generated/error_verifier.dart';
@@ skipping 1063 matching lines @@
     return token;
   }
 
   void _shiftTokens(Token token) {
     while (token != null) {
       if (token.offset > _updateOffset) {
         token.offset += _updateDelta;
       }
       // comments
       _shiftTokens(token.precedingComments);
-      if (token is CommentToken) {
+      if (token is DocumentationCommentToken) {
         for (Token reference in token.references) {
           _shiftTokens(reference);
         }
       }
       // next
       if (token.type == TokenType.EOF) {
         break;
       }
       token = token.next;
     }
@@ skipping 449 matching lines @@
   }
 }
 
 
 class _TokenPair {
   final Token oldToken;
   final Token newToken;
   final bool atComment;
   _TokenPair(this.oldToken, this.newToken, [this.atComment = false]);
 }