Move incremental scanner to separate file

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index 5cf4b622b9c196b4a7832cd8641a75be1d1f5743..e1c769241d88b78bbca6fdf0eb3c61a9d872b246 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -2,14 +2,12 @@
 // 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.
 
-// This code was auto-generated, is not intended to be edited, and is subject to
-// significant change. Please see the README file for more information.
-
 library engine.parser_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/error.dart';
+import 'package:analyzer/src/generated/incremental_scanner.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart' show Source;