Add dummy dart:html library for documentation.

lib/html/doc/interface/XPathResult.dartdoc

+// 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:
+//   This file contains documentation that is merged into the real source.
+//   Do not make code changes here.
+
+/// @domName XPathResult
+interface XPathResult {
+
+  static final int ANY_TYPE = 0;
+
+  static final int ANY_UNORDERED_NODE_TYPE = 8;
+
+  static final int BOOLEAN_TYPE = 3;
+
+  static final int FIRST_ORDERED_NODE_TYPE = 9;
+
+  static final int NUMBER_TYPE = 1;
+
+  static final int ORDERED_NODE_ITERATOR_TYPE = 5;
+
+  static final int ORDERED_NODE_SNAPSHOT_TYPE = 7;
+
+  static final int STRING_TYPE = 2;
+
+  static final int UNORDERED_NODE_ITERATOR_TYPE = 4;
+
+  static final int UNORDERED_NODE_SNAPSHOT_TYPE = 6;
+
+  /** @domName XPathResult.booleanValue */
+  final bool booleanValue;
+
+  /** @domName XPathResult.invalidIteratorState */
+  final bool invalidIteratorState;
+
+  /** @domName XPathResult.numberValue */
+  final num numberValue;
+
+  /** @domName XPathResult.resultType */
+  final int resultType;
+
+  /** @domName XPathResult.singleNodeValue */
+  final Node singleNodeValue;
+
+  /** @domName XPathResult.snapshotLength */
+  final int snapshotLength;
+
+  /** @domName XPathResult.stringValue */
+  final String stringValue;
+
+  /** @domName XPathResult.iterateNext */
+  Node iterateNext();
+
+  /** @domName XPathResult.snapshotItem */
+  Node snapshotItem(int index);
+}