skip comments in benchmark code

pkg/analyzer_cli/tool/perf.dart

Index: pkg/analyzer_cli/tool/perf.dart
diff --git a/pkg/analyzer_cli/tool/perf.dart b/pkg/analyzer_cli/tool/perf.dart
index 2b7932c0d0ba12dc33d731d5d278d877e551ef2f..40a747ab1e27e473bb416b1f1b48c6ff7dc63293 100644
--- a/pkg/analyzer_cli/tool/perf.dart
+++ b/pkg/analyzer_cli/tool/perf.dart
@@ -187,7 +187,7 @@ Token tokenize(Source source) {
   // 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);
+      AnalysisErrorListener.NULL_LISTENER)..preserveComments = false;
   var token = scanner.tokenize();
   scanTimer.stop();
   return token;