Add a Resource.parent getter, which gets the parent directory.

pkg/analysis_server/test/physical_resource_provider_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.physical.resource.provider;
 
 import 'dart:async';
 import 'dart:io' as io;
 
 import 'package:analysis_server/src/resource.dart';
@@ skipping 142 matching lines @@
           file.hashCode;
         });
 
         test('shortName', () {
           expect(file.shortName, 'file.txt');
         });
 
         test('toString', () {
           expect(file.toString(), path);
         });
+
+        test('parent', () {
+          Resource parent = file.parent;
+          expect(parent, new isInstanceOf<Folder>());
+          expect(parent.path, equals(tempPath));
+        });
       });
 
       group('Folder', () {
         String path;
         Folder folder;
 
         setUp(() {
           path = join(tempPath, 'folder');
           new io.Directory(path).createSync();
           folder = PhysicalResourceProvider.INSTANCE.getResource(path);
@@ skipping 36 matching lines @@
           });
           // check names
           expect(children[0].shortName, 'a.txt');
           expect(children[1].shortName, 'bFolder');
           expect(children[2].shortName, 'c.txt');
           // check types
           expect(children[0], _isFile);
           expect(children[1], _isFolder);
           expect(children[2], _isFile);
         });
+
+        test('parent', () {
+          Resource parent = folder.parent;
+          expect(parent, new isInstanceOf<Folder>());
+          expect(parent.path, equals(tempPath));
+
+          // Since the OS is in control of where tempPath is, we don't know how
+          // far it should be from the root.  So just verify that each call to
+          // parent results in a a folder with a shorter path, and that we
+          // reach the root eventually.
+          while (true) {
+            Resource grandParent = parent.parent;
+            if (grandParent == null) {
+              break;
+            }
+            expect(grandParent, new isInstanceOf<Folder>());
+            expect(grandParent.path.length, lessThan(parent.path.length));
+            parent = grandParent;
+          }
+        });
       });
     });
 }
 
 var _isFile = new isInstanceOf<File>();
 var _isFolder = new isInstanceOf<Folder>();
 var _isMemoryResourceException = new isInstanceOf<MemoryResourceException>();