fasta scanner recovery and error code translation improvements

pkg/front_end/tool/fasta_perf.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.
 
 /// An entrypoint used to run portions of fasta and measure its performance.
 library front_end.tool.fasta_perf;
 
 import 'dart:async';
 import 'dart:io';
 
@@ skipping 150 matching lines @@
   var listener = new DirectiveListener();
   new DirectiveParser(listener).parseUnit(tokenize(contents));
   return listener.uris;
 }
 
 /// Diet parser that stops eagerly at the first sign that we have seen all the
 /// import, export, and part directives.
 class DirectiveParser extends ClassMemberParser {
   DirectiveParser(listener) : super(listener);
 
-  static final _endToken = new SymbolToken(EOF_INFO, -1);
+  static final _endToken = new SymbolToken.eof(-1);
 
   Token parseClassOrNamedMixinApplication(Token token) => _endToken;
   Token parseEnum(Token token) => _endToken;
   parseTypedef(token) => _endToken;
   parseTopLevelMember(Token token) => _endToken;
 }
 
 /// Listener that records the URIs from imports, exports, and part directives.
 class DirectiveListener extends Listener {
   bool _inDirective = false;
@@ skipping 106 matching lines @@
 /// Report that metric [name] took [time] micro-seconds to process
 /// [inputSize] characters.
 void report(String name, int time) {
   var sb = new StringBuffer();
   var padding = ' ' * (20 - name.length);
   sb.write('$name:$padding $time us, ${time ~/ 1000} ms');
   var invSpeed = (time * 1000 / inputSize).toStringAsFixed(2);
   sb.write(', $invSpeed ns/char');
   print('$sb');
 }