Use kernel transformation and VmTarget.

pkg/front_end/lib/src/fasta/analyzer/token_utils.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.
 
 library fasta.analyzer.token_utils;
 
 import 'package:front_end/src/fasta/parser/error_kind.dart' show
     ErrorKind;
 
 import 'package:front_end/src/fasta/scanner/error_token.dart' show
-    ErrorToken,
-    UnmatchedToken;
+    ErrorToken;
 
 import 'package:front_end/src/fasta/scanner/keyword.dart' show
     Keyword;
 
 import 'package:front_end/src/fasta/scanner/precedence.dart';
 
 import 'package:front_end/src/fasta/scanner/token.dart' show
     BeginGroupToken,
     KeywordToken,
     StringToken,
@@ skipping 613 matching lines @@
     case BACKSLASH_TOKEN: return TokenType.BACKSLASH;
     case PERIOD_PERIOD_PERIOD_TOKEN: return TokenType.PERIOD_PERIOD_PERIOD;
     // case GENERIC_METHOD_TYPE_LIST_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_LIST;
     // case GENERIC_METHOD_TYPE_ASSIGN_TOKEN:
     //   return TokenType.GENERIC_METHOD_TYPE_ASSIGN;
     default:
       return internalError("Unhandled token ${token.info}");
   }
 }