Move byte_store.dart and file_byte_store.dart to their own subdirectory.

pkg/front_end/test/src/byte_store/byte_store_test.dart

Index: pkg/front_end/test/src/byte_store/byte_store_test.dart
diff --git a/pkg/front_end/test/src/incremental/byte_store_test.dart b/pkg/front_end/test/src/byte_store/byte_store_test.dart
similarity index 98%
rename from pkg/front_end/test/src/incremental/byte_store_test.dart
rename to pkg/front_end/test/src/byte_store/byte_store_test.dart
index 729667935f1e1bcdf0228e75d594141ef54c3585..2ebc02450852476582ace553113422df1b300a4f 100644
--- a/pkg/front_end/test/src/incremental/byte_store_test.dart
+++ b/pkg/front_end/test/src/byte_store/byte_store_test.dart
@@ -2,7 +2,7 @@
 // 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:front_end/src/incremental/byte_store.dart';
+import 'package:front_end/src/byte_store/byte_store.dart';
 import 'package:mockito/mockito.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';