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

pkg/analyzer/test/generated/parser_fasta_test.dart

Index: pkg/analyzer/test/generated/parser_fasta_test.dart
diff --git a/pkg/analyzer/test/generated/parser_fasta_test.dart b/pkg/analyzer/test/generated/parser_fasta_test.dart
index b3eed49af26235c139c10ada1d7b7120581a7193..e69b7ac9b5bb581416f896e5744a74045c97a1d4 100644
--- a/pkg/analyzer/test/generated/parser_fasta_test.dart
+++ b/pkg/analyzer/test/generated/parser_fasta_test.dart
@@ -13,9 +13,8 @@ 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';