switch perf tool to use scanner in front_end

pkg/front_end/tool/perf.dart

Index: pkg/front_end/tool/perf.dart
diff --git a/pkg/front_end/tool/perf.dart b/pkg/front_end/tool/perf.dart
index ec306caf644c524656e26d9c687eef8ef50b2d3c..4d61e9bdfb5f6e5cdce755ef7172cd241d0d97a9 100644
--- a/pkg/front_end/tool/perf.dart
+++ b/pkg/front_end/tool/perf.dart
@@ -9,15 +9,12 @@ 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';
@@ -26,6 +23,10 @@ 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;
 
@@ -205,13 +206,23 @@ Token tokenize(Source source) {
   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) {