fix fasta/analyzer KeywordToken.value()

pkg/analyzer/lib/src/dart/scanner/scanner.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.dart.scanner.scanner;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/error/syntactic_errors.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:front_end/src/fasta/scanner.dart' as fasta;
-import 'package:front_end/src/fasta/scanner/abstract_scanner.dart'
-    show fastaSupportsGenericMethodComments;
 import 'package:front_end/src/fasta/scanner/precedence.dart' as fasta;
 import 'package:front_end/src/scanner/errors.dart' show translateErrorToken;
 import 'package:front_end/src/scanner/scanner.dart' as fe;
 import 'package:front_end/src/scanner/token.dart' show Token;
 
 export 'package:analyzer/src/dart/error/syntactic_errors.dart';
 export 'package:front_end/src/scanner/scanner.dart' show KeywordState;
 
 /**
  * The class `Scanner` implements a scanner for Dart code.
@@ skipping 139 matching lines @@
     }
     firstToken = token;
     return firstToken;
   }
 
   @override
   set preserveComments(bool preserveComments) {
     this._preserveComments = preserveComments;
   }
 }