Handle "is" and "as" like other keywords.

dart/lib/compiler/implementation/scanner/keyword.dart

 // Copyright (c) 2011, 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.
 
 /**
  * A keyword in the Dart programming language.
  */
 class Keyword implements SourceString {
   static const List<Keyword> values = const <Keyword> [
       const Keyword("break"),
       const Keyword("case"),
       const Keyword("catch"),
       const Keyword("class"),
       const Keyword("const"),
       const Keyword("continue"),
       const Keyword("default"),
       const Keyword("do"),
       const Keyword("else"),
       const Keyword("extends"),
       const Keyword("false"),
       const Keyword("final"),
       const Keyword("finally"),
       const Keyword("for"),
       const Keyword("if"),
       const Keyword("in"),
+      // TODO(ahe): Don't think this is a reserved word.
+      // See: http://dartbug.com/5579
       const Keyword("is", info: IS_INFO),
       const Keyword("new"),
       const Keyword("null"),
       const Keyword("return"),
       const Keyword("super"),
       const Keyword("switch"),
       const Keyword("this"),
       const Keyword("throw"),
       const Keyword("true"),
       const Keyword("try"),
@@ skipping 179 matching lines @@
   final Keyword keyword;
 
   LeafKeywordState(String syntax) : keyword = Keyword.keywords[syntax];
 
   bool isLeaf() => true;
 
   KeywordState next(int c) => null;
 
   String toString() => keyword.syntax;
 }