Properly exposing NodeIterator and TreeWalker.

tests/html/node_test.dart

 // Copyright (c) 2011, 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 NodeTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 import 'dart:svg' as svg;
 
@@ skipping 329 matching lines @@
       expect(filtered, isNodeList);
     });
 
     test('sublist', () {
       var range = makeNodeList().sublist(1, 3);
       expect(range, isNodeList);
       expect(range[0], isBRElement);
       expect(range[1], isComment);
     });
   });
+
+  group('iterating', () {
+    test('NodeIterator', () {
+      var root = makeNodeWithChildren();
+      var nodeIterator = new NodeIterator(root, NodeFilter.SHOW_COMMENT);
+      expect(nodeIterator.nextNode(), isComment);
+      expect(nodeIterator.nextNode(), isNull);
+    });
+
+    test('TreeWalker', () {
+      var root = makeNodeWithChildren();
+      var treeWalker = new TreeWalker(root, NodeFilter.SHOW_COMMENT);
+      expect(treeWalker.nextNode(), isComment);
+      expect(treeWalker.nextNode(), isNull);
+    });
+  });
 }