cleanup fasta token classes

pkg/front_end/lib/src/fasta/scanner/recover.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 licenset hat can be found in the LICENSE file.
 
 library fasta.scanner.recover;
 
 import '../../scanner/token.dart' show TokenType;
 
 import '../fasta_codes.dart'
     show
         FastaCode,
         codeAsciiControlCharacter,
         codeEncoding,
         codeExpectedHexDigit,
         codeMissingExponent,
         codeNonAsciiIdentifier,
         codeNonAsciiWhitespace,
         codeUnexpectedDollarInString,
         codeUnmatchedToken,
         codeUnterminatedComment,
         codeUnterminatedString;
 
 import '../../scanner/token.dart' show Token;
 
-import 'token.dart' show StringToken, SymbolToken;
+import 'token.dart' show StringToken;
 
 import 'error_token.dart' show NonAsciiIdentifierToken, ErrorToken;
 
 /// Recover from errors in [tokens]. The original sources are provided as
 /// [bytes]. [lineStarts] are the beginning character offsets of lines, and
 /// must be updated if recovery is performed rewriting the original source
 /// code.
 Token defaultRecoveryStrategy(
     List<int> bytes, Token tokens, List<int> lineStarts) {
   // See [Parser.reportErrorToken](../parser/src/parser.dart) for how
@@ skipping 173 matching lines @@
     if (goodTail == null) {
       good = current;
     } else {
       goodTail.next = current;
       current.previous = goodTail;
     }
     beforeGoodTail = goodTail;
     goodTail = current;
   }
 
-  error.previous = new SymbolToken.eof(-1)..next = error;
+  error.previous = new Token.eof(-1)..next = error;
   Token tail;
   if (good != null) {
     errorTail.next = good;
     good.previous = errorTail;
     tail = goodTail;
   } else {
     tail = errorTail;
   }
-  if (!tail.isEof) tail.next = new SymbolToken.eof(tail.end)..previous = tail;
+  if (!tail.isEof) tail.next = new Token.eof(tail.end)..previous = tail;
   return error;
 }
 
 Token synthesizeToken(int charOffset, String value, TokenType type) {
   return new StringToken.fromString(type, value, charOffset);
 }
 
 Token skipToEof(Token token) {
   while (!token.isEof) {
     token = token.next;
   }
   return token;
 }
 
 String closeBraceFor(String openBrace) {
   return const {
     '(': ')',
     '[': ']',
     '{': '}',
     '<': '>',
     r'${': '}',
   }[openBrace];
 }