Move parser helper classes to own files and clean them up.

pkg/analyzer/test/generated/parser_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/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart' as analyzer;
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/fasta/ast_builder.dart';
 import 'package:analyzer/src/generated/parser.dart' as analyzer;
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:analyzer/src/string_source.dart';
 import 'package:front_end/src/fasta/fasta_codes.dart' show Message;
 import 'package:front_end/src/fasta/kernel/kernel_builder.dart';
 import 'package:front_end/src/fasta/kernel/kernel_library_builder.dart';
-import 'package:front_end/src/fasta/parser/identifier_context.dart'
-    show IdentifierContext;
-import 'package:front_end/src/fasta/parser/parser.dart' as fasta;
+import 'package:front_end/src/fasta/parser.dart' show IdentifierContext;
+import 'package:front_end/src/fasta/parser.dart' as fasta;
 import 'package:front_end/src/fasta/scanner/string_scanner.dart';
 import 'package:front_end/src/fasta/scanner/token.dart' as fasta;
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'parser_fasta_listener.dart';
 import 'parser_test.dart';
 import 'test_support.dart';
 
 main() {
@@ skipping 922 matching lines @@
   }
 
   @override
   @failingTest
   void test_parsePartOfDirective_uri() {
     // TODO(paulberry,ahe): URIs in "part of" declarations are not supported by
     // Fasta.
     super.test_parsePartOfDirective_uri();
   }
 }