fasta tokens implement analyzer token API

pkg/front_end/test/scanner_fasta_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/fasta/scanner/abstract_scanner.dart'
+    show fastaSupportsGenericMethodComments;
 import 'package:front_end/src/fasta/scanner/error_token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/keyword.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/token_constants.dart' as fasta;
 import 'package:front_end/src/scanner/errors.dart';
 import 'package:front_end/src/scanner/token.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'scanner_test.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ScannerTest_Fasta);
     defineReflectiveTests(ScannerTest_Fasta_Direct);
     defineReflectiveTests(ScannerTest_Fasta_Roundtrip);
   });
 }
 
 @reflectiveTest
 class ScannerTest_Fasta extends ScannerTestBase {
   @override
   Token scanWithListener(String source, ErrorListener listener,
       {bool genericMethodComments: false,
       bool lazyAssignmentOperators: false}) {
-    if (genericMethodComments) {
+    if (genericMethodComments && !fastaSupportsGenericMethodComments) {
       // Fasta doesn't support generic method comments.
       // TODO(paulberry): once the analyzer toolchain no longer needs generic
       // method comments, remove tests that exercise them.
       fail('No generic method comment support in Fasta');
     }
     // Note: Fasta always supports lazy assignment operators (`&&=` and `||=`),
     // so we can ignore the `lazyAssignmentOperators` flag.
     // TODO(paulberry): once lazyAssignmentOperators are fully supported by
     // Dart, remove this flag.
     var scanner = new fasta.StringScanner(source, includeComments: true);
@@ skipping 473 matching lines @@
   final ErrorListener _listener;
 
   ToAnalyzerTokenStreamConverter_WithListener(this._listener);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     _listener.errors.add(new TestError(offset, errorCode, arguments));
   }
 }