flatten token hierarchy

pkg/analyzer/lib/src/dart/ast/token.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 analyzer.src.dart.ast.token;
 
 export 'package:front_end/src/scanner/token.dart'
     show
         BeginToken,
-        BeginTokenWithComment,
         CommentToken,
         DocumentationCommentToken,
         KeywordToken,
-        KeywordTokenWithComment,
         SimpleToken,
         StringToken,
-        StringTokenWithComment,
         SyntheticKeywordToken,
         SyntheticStringToken,
-        TokenClass,
-        TokenWithComment;
+        TokenClass;