fix fasta/analyzer KeywordToken.value()

pkg/front_end/lib/src/scanner/token.dart

 // Copyright (c) 2016, 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.
 
 /**
  * Defines the tokens that are produced by the scanner, used by the parser, and
  * referenced from the [AST structure](ast.dart).
  */
 import 'dart:collection';
 
@@ skipping 340 matching lines @@
    */
   KeywordToken(this.keyword, int offset) : super(TokenType.KEYWORD, offset);
 
   @override
   String get lexeme => keyword.syntax;
 
   @override
   Token copy() => new KeywordToken(keyword, offset);
 
   @override
-  Keyword value() => keyword;
+  // Changed return type from Keyword to Object because
+  // fasta considers pseudo-keywords to be keywords rather than identifiers
+  Object value() => keyword;
 }
 
 /**
  * A keyword token that is preceded by comments.
  */
 class KeywordTokenWithComment extends KeywordToken implements TokenWithComment {
   /**
    * The first comment in the list of comments that precede this token.
    */
   @override
@@ skipping 816 matching lines @@
 
   void set precedingComments(CommentToken comment) {
     _precedingComment = comment;
     _setCommentParent(_precedingComment);
   }
 
   @override
   Token copy() =>
       new TokenWithComment(type, offset, copyComments(precedingComments));
 }