Move file_system libraries into 'analyzer'.

pkg/analysis_server/test/context_directory_manager_test.dart

 // Copyright (c) 2014, 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.
 
 library test.context.directory.manager;
 
 import 'mocks.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analysis_server/src/context_directory_manager.dart';
 import 'package:analysis_server/src/package_map_provider.dart';
-import 'package:analysis_server/src/resource.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 
 class TestContextDirectoryManager extends ContextDirectoryManager {
   TestContextDirectoryManager(
       MemoryResourceProvider resourceProvider, PackageMapProvider packageMapProvider)
       : super(resourceProvider, packageMapProvider);
 
@@ skipping 279 matching lines @@
         packageMapProvider.packageMap = null;
         resourceProvider.modifyFile(dependencyPath, 'new contents');
         return pumpEventQueue().then((_) {
           // The package map should have been changed to null.
           expect(manager.currentContextPackageMaps[projPath], isNull);
         });
       });
     });
   });
 }