flag to enable fasta scanner in analyzer

pkg/front_end/test/scanner_roundtrip_test.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.
 
 import 'package:analyzer/src/fasta/token_utils.dart';
 import 'package:front_end/src/scanner/errors.dart' as analyzer;
 import 'package:front_end/src/scanner/reader.dart' as analyzer;
 import 'package:front_end/src/scanner/scanner.dart' as analyzer;
 import 'package:front_end/src/scanner/token.dart';
 import 'package:test/test.dart';
@@ skipping 58 matching lines @@
   @override
   @failingTest
   void test_comment_generic_method_type_list() {
     // TODO(paulberry,ahe): Fasta scanner doesn't support generic comment
     // syntax.
     super.test_comment_generic_method_type_list();
   }
 }
 
 class TestScanner extends analyzer.Scanner {
-  TestScanner(analyzer.CharacterReader reader) : super(reader);
+  TestScanner(analyzer.CharacterReader reader) : super.create(reader);
 
   @override
   void reportError(
       analyzer.ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     fail('Unexpected error $errorCode while scanning offset $offset\n'
         '   arguments: $arguments');
   }
 }