cleanup fasta token classes

pkg/front_end/test/token_test.dart

 // Copyright (c) 2017, 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.
 
 import 'package:front_end/src/fasta/scanner/string_scanner.dart';
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/scanner/token.dart';
 import 'package:front_end/src/scanner/errors.dart' as analyzer;
 import 'package:front_end/src/scanner/reader.dart' as analyzer;
 import 'package:front_end/src/scanner/scanner.dart' as analyzer;
@@ skipping 86 matching lines @@
     var token2 = analyzerScanner.tokenize();
 
     bool stringTokenFound = false;
     bool keywordTokenFound = false;
     bool symbolTokenFound = false;
     bool beginGroupTokenFound = false;
 
     while (!token1.isEof) {
       if (token1 is fasta.StringToken) stringTokenFound = true;
       if (token1 is KeywordToken) keywordTokenFound = true;
-      if (token1 is fasta.SymbolToken) symbolTokenFound = true;
-      if (token1 is fasta.BeginGroupToken) beginGroupTokenFound = true;
+      if (token1.type == TokenType.OPEN_PAREN) symbolTokenFound = true;
+      if (token1 is BeginToken) beginGroupTokenFound = true;
 
       var copy1 = token1.copy();
       expect(copy1, isNotNull);
 
       var copy2 = token2.copy();
       expect(copy2, isNotNull);
 
       assertCopiedToken(copy1, copy2);
 
       token1 = token1.next;
@@ skipping 94 matching lines @@
 class TestScanner extends analyzer.Scanner {
   TestScanner(analyzer.CharacterReader reader) : super.create(reader);
 
   @override
   void reportError(
       analyzer.ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     fail('Unexpected error $errorCode while scanning offset $offset\n'
         '   arguments: $arguments');
   }
 }