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

pkg/analyzer/test/src/dart/analysis/base.dart

 // Copyright (c) 2016, 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/element/element.dart';
 import 'package:analyzer/dart/element/visitor.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/analysis/file_state.dart';
 import 'package:analyzer/src/dart/analysis/status.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisOptionsImpl;
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/package_bundle_reader.dart';
 import 'package:front_end/src/base/performace_logger.dart';
-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 '../../context/mock_sdk.dart';
 
 /**
  * Finds an [Element] with the given [name].
  */
 Element findChildElement(Element root, String name, [ElementKind kind]) {
   Element result = null;
@@ skipping 127 matching lines @@
 
   _ElementVisitorFunctionWrapper(this.function);
 
   visitElement(Element element) {
     function(element);
     super.visitElement(element);
   }
 }
 
 class _GeneratedUriResolverMock extends Mock implements UriResolver {}