Add dummy dart:html library for documentation.

lib/html/doc/interface/IDBTransaction.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 IDBTransaction
+interface IDBTransaction extends EventTarget {
+
+  /**
+   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
+   */
+  IDBTransactionEvents get on();
+
+  static final int READ_ONLY = 0;
+
+  static final int READ_WRITE = 1;
+
+  static final int VERSION_CHANGE = 2;
+
+  /** @domName IDBTransaction.db */
+  final IDBDatabase db;
+
+  /** @domName IDBTransaction.error */
+  final DOMError error;
+
+  /** @domName IDBTransaction.mode */
+  final String mode;
+
+  /** @domName IDBTransaction.abort */
+  void abort();
+
+  /** @domName IDBTransaction.addEventListener */
+  void $dom_addEventListener(String type, EventListener listener, [bool useCapture]);
+
+  /** @domName IDBTransaction.dispatchEvent */
+  bool $dom_dispatchEvent(Event evt);
+
+  /** @domName IDBTransaction.objectStore */
+  IDBObjectStore objectStore(String name);
+
+  /** @domName IDBTransaction.removeEventListener */
+  void $dom_removeEventListener(String type, EventListener listener, [bool useCapture]);
+}
+
+interface IDBTransactionEvents extends Events {
+
+  EventListenerList get abort();
+
+  EventListenerList get complete();
+
+  EventListenerList get error();
+}