update fasta scanner to generate two types of comments

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 881 matching lines @@
   static const TokenType DOUBLE = fasta.DOUBLE_INFO;
 
   static const TokenType HEXADECIMAL = fasta.HEXADECIMAL_INFO;
 
   static const TokenType IDENTIFIER = fasta.IDENTIFIER_INFO;
 
   static const TokenType INT = fasta.INT_INFO;
 
   static const TokenType KEYWORD = fasta.KEYWORD_INFO;
 
-  static const TokenType MULTI_LINE_COMMENT =
-      const fasta.PrecedenceInfo(null, 'MULTI_LINE_COMMENT', 0, -1);
+  static const TokenType MULTI_LINE_COMMENT = fasta.MULTI_LINE_COMMENT_INFO;
 
   static const TokenType SCRIPT_TAG = fasta.SCRIPT_INFO;
 
-  static const TokenType SINGLE_LINE_COMMENT =
-      const fasta.PrecedenceInfo(null, 'SINGLE_LINE_COMMENT', 0, -1);
+  static const TokenType SINGLE_LINE_COMMENT = fasta.SINGLE_LINE_COMMENT_INFO;
 
   static const TokenType STRING = fasta.STRING_INFO;
 
   static const TokenType AMPERSAND = fasta.AMPERSAND_INFO;
 
   static const TokenType AMPERSAND_AMPERSAND = fasta.AMPERSAND_AMPERSAND_INFO;
 
   static const TokenType AMPERSAND_AMPERSAND_EQ =
       const fasta.PrecedenceInfo('&&=', 'AMPERSAND_AMPERSAND_EQ', 1, -1);
 
@@ skipping 239 matching lines @@
 
   void set precedingComments(CommentToken comment) {
     _precedingComment = comment;
     _setCommentParent(_precedingComment);
   }
 
   @override
   Token copy() =>
       new TokenWithComment(type, offset, copyComments(precedingComments));
 }