Add dummy dart:html library for documentation.

lib/html/doc/interface/IDBVersionChangeRequest.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 IDBVersionChangeRequest
+interface IDBVersionChangeRequest extends IDBRequest, EventTarget {
+
+  /**
+   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
+   */
+  IDBVersionChangeRequestEvents get on();
+}
+
+interface IDBVersionChangeRequestEvents extends IDBRequestEvents {
+
+  EventListenerList get blocked();
+}