cleanup fasta token classes

pkg/analyzer/lib/src/fasta/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/scanner/token.dart' show Token;
 
-import 'package:front_end/src/fasta/scanner/token.dart' show SymbolToken;
-
 import 'package:front_end/src/fasta/scanner/token_constants.dart';
 
 import 'package:front_end/src/scanner/errors.dart' show translateErrorToken;
 
 import 'package:front_end/src/scanner/errors.dart' as analyzer
     show ScannerErrorCode;
 
 /// Class capable of converting a stream of Fasta tokens to a stream of analyzer
 /// tokens.
 ///
 /// This is a class rather than an ordinary method so that it can be subclassed
 /// in tests.
 class ToAnalyzerTokenStreamConverter {
   /// Converts a stream of Fasta tokens (starting with [token] and continuing to
   /// EOF) to a stream of analyzer tokens. This modifies the fasta token stream
   /// to be an analyzer token stream by removing error tokens and reporting
   /// those errors to the associated error listener.
   Token convertTokens(Token firstToken) {
-    Token previous = new SymbolToken.eof(-1);
+    Token previous = new Token.eof(-1);
     Token token = firstToken;
     token.previous = previous;
     previous.next = token;
     while (!token.isEof) {
       if (token.type.kind == BAD_INPUT_TOKEN) {
         translateErrorToken(token, reportError);
         previous.next = token.next;
         token.next.previous = previous;
       } else {
         previous = token;
       }
       token = token.next;
     }
     return firstToken;
   }
 
   /// Handles an error found during [convertTokens].
   ///
   /// Intended to be overridden by derived classes; by default, does nothing.
   void reportError(analyzer.ScannerErrorCode errorCode, int offset,
       List<Object> arguments) {}
 }