switch perf tool to use scanner in front_end

pkg/front_end/tool/perf.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.
 
 /// An entrypoint used to run portions of front_end and measure its performance.
 library front_end.tool.perf;
 
 import 'dart:async';
 import 'dart:io' show exit, stderr;
 
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/file_system/file_system.dart' show ResourceUriResolver;
 import 'package:analyzer/file_system/physical_file_system.dart'
     show PhysicalResourceProvider;
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/context/builder.dart';
-import 'package:analyzer/src/dart/scanner/reader.dart';
-import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/dart/sdk/sdk.dart' show FolderBasedDartSdk;
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:kernel/analyzer/loader.dart';
 import 'package:kernel/kernel.dart';
 import 'package:package_config/discovery.dart';
 
+import 'package:front_end/src/scanner/reader.dart';
+import 'package:front_end/src/scanner/scanner.dart';
+import 'package:front_end/src/scanner/token.dart';
+
 /// Cumulative total number of chars scanned.
 int scanTotalChars = 0;
 
 /// Cumulative time spent scanning.
 Stopwatch scanTimer = new Stopwatch();
 
 /// Factory to load and resolve app, packages, and sdk sources.
 SourceFactory sources;
 
 main(List<String> args) async {
@@ skipping 159 matching lines @@
   return parser.parseCompilationUnit(token);
 }
 
 /// Scan [source] and return the first token produced by the scanner.
 Token tokenize(Source source) {
   scanTimer.start();
   var contents = source.contents.data;
   scanTotalChars += contents.length;
   // TODO(sigmund): is there a way to scan from a random-access-file without
   // first converting to String?
-  var scanner = new Scanner(source, new CharSequenceReader(contents),
-      AnalysisErrorListener.NULL_LISTENER)..preserveComments = false;
+  var scanner = new _Scanner(contents);
   var token = scanner.tokenize();
   scanTimer.stop();
   return token;
 }
 
+class _Scanner extends Scanner {
+  _Scanner(String contents) : super(new CharSequenceReader(contents)) {
+    preserveComments = false;
+  }
+
+  @override
+  void reportError(errorCode, int offset, List<Object> arguments) {
+    // ignore errors.
+  }
+}
+
 /// Report that metric [name] took [time] micro-seconds to process
 /// [scanTotalChars] characters.
 void report(String name, int time) {
   var sb = new StringBuffer();
   sb.write('$name: $time us, ${time ~/ 1000} ms');
   sb.write(', ${scanTotalChars * 1000 ~/ time} chars/ms');
   print('$sb');
 }
 
 // TODO(sigmund): replace this once kernel is produced by the frontend directly.
@@ skipping 11 matching lines @@
     const int errorLimit = 100;
     stderr.writeln(errors.take(errorLimit).join('\n'));
     if (errors.length > errorLimit) {
       stderr.writeln('[error] ${errors.length - errorLimit} errors not shown');
     }
   }
   dartkTimer.stop();
   report("kernel_gen_e2e", dartkTimer.elapsedMicroseconds);
   return program;
 }