Fix for the watcher leak.

pkg/analysis_server/test/context_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 'dart:collection';
 
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 1105 matching lines @@
     expect(callbacks.currentContextPaths, hasLength(0));
     expect(callbacks.currentContextFilePaths, hasLength(0));
   }
 
   void test_setRoots_removeFolderWithPackagespec() {
     // create a pubspec
     String pubspecPath = posix.join(projPath, '.packages');
     resourceProvider.newFile(pubspecPath, '');
     // add one root - there is a context
     manager.setRoots(<String>[projPath], <String>[], <String, String>{});
+    expect(manager.changeSubscriptions, hasLength(1));
     expect(callbacks.currentContextPaths, hasLength(1));
     // set empty roots - no contexts
     manager.setRoots(<String>[], <String>[], <String, String>{});
+    expect(manager.changeSubscriptions, hasLength(0));
     expect(callbacks.currentContextPaths, hasLength(0));
     expect(callbacks.currentContextFilePaths, hasLength(0));
   }
 
   void test_setRoots_removeFolderWithPackagespecFolder() {
     // prepare paths
     String projectA = '/projectA';
     String projectB = '/projectB';
     String subProjectA = '$projectA/sub';
     String subProjectB = '$projectB/sub';
@@ skipping 852 matching lines @@
 class TestUriResolver extends UriResolver {
   Map<Uri, Source> uriMap;
 
   TestUriResolver(this.uriMap);
 
   @override
   Source resolveAbsolute(Uri uri, [Uri actualUri]) {
     return uriMap[uri];
   }
 }