Add dummy dart:html library for documentation.

lib/html/doc/interface/NodeIterator.dart

+// Copyright (c) 2012, 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.
+
+// WARNING: Do not edit - generated code.
+
+/// @domName NodeIterator
+interface NodeIterator {
+
+  /** @domName NodeIterator.expandEntityReferences */
+  final bool expandEntityReferences;
+
+  /** @domName NodeIterator.filter */
+  final NodeFilter filter;
+
+  /** @domName NodeIterator.pointerBeforeReferenceNode */
+  final bool pointerBeforeReferenceNode;
+
+  /** @domName NodeIterator.referenceNode */
+  final Node referenceNode;
+
+  /** @domName NodeIterator.root */
+  final Node root;
+
+  /** @domName NodeIterator.whatToShow */
+  final int whatToShow;
+
+  /** @domName NodeIterator.detach */
+  void detach();
+
+  /** @domName NodeIterator.nextNode */
+  Node nextNode();
+
+  /** @domName NodeIterator.previousNode */
+  Node previousNode();
+}