flag to enable fasta scanner in analyzer

pkg/front_end/test/src/base/libraries_reader_test.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.
 
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/summary/summarize_ast.dart';
 import 'package:front_end/src/base/library_info.dart';
 import 'package:front_end/src/libraries_reader.dart';
 import 'package:front_end/src/scanner/errors.dart';
@@ skipping 209 matching lines @@
   LibraryInfo _computeSingleInfo(String text,
       {String additionalDeclarations: ''}) {
     var libraries = _computeLibraries(
         'const Map<String, LibraryInfo> libraries = const { "x": $text };',
         additionalDeclarations: additionalDeclarations);
     return libraries['x'];
   }
 }
 
 class _Scanner extends Scanner {
-  _Scanner(String contents) : super(new CharSequenceReader(contents)) {
+  _Scanner(String contents) : super.create(new CharSequenceReader(contents)) {
     preserveComments = false;
   }
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     fail('Unexpected error($errorCode, $offset, $arguments)');
   }
 }