Remove unused TokenType.IS.

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 982 matching lines @@
 
   static const TokenType HASH =
       const TokenType._('HASH', TokenClass.NO_CLASS, '#');
 
   static const TokenType INDEX =
       const TokenType._('INDEX', TokenClass.UNARY_POSTFIX_OPERATOR, '[]');
 
   static const TokenType INDEX_EQ =
       const TokenType._('INDEX_EQ', TokenClass.UNARY_POSTFIX_OPERATOR, '[]=');
 
-  static const TokenType IS =
-      const TokenType._('IS', TokenClass.RELATIONAL_OPERATOR, 'is');
-
   static const TokenType LT =
       const TokenType._('LT', TokenClass.RELATIONAL_OPERATOR, '<');
 
   static const TokenType LT_EQ =
       const TokenType._('LT_EQ', TokenClass.RELATIONAL_OPERATOR, '<=');
 
   static const TokenType LT_LT =
       const TokenType._('LT_LT', TokenClass.SHIFT_OPERATOR, '<<');
 
   static const TokenType LT_LT_EQ =
@@ skipping 272 matching lines @@
  */
 class _EndOfFileTokenType extends TokenType {
   /**
    * Initialize a newly created token.
    */
   const _EndOfFileTokenType() : super._('EOF', TokenClass.NO_CLASS, '');
 
   @override
   String toString() => '-eof-';
 }