Add dummy dart:html library for documentation.

lib/html/doc/interface/JavaScriptAudioNode.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 JavaScriptAudioNode
+interface JavaScriptAudioNode extends AudioNode, EventTarget {
+
+  /**
+   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
+   */
+  JavaScriptAudioNodeEvents get on();
+
+  /** @domName JavaScriptAudioNode.bufferSize */
+  final int bufferSize;
+}
+
+interface JavaScriptAudioNodeEvents extends Events {
+
+  EventListenerList get audioProcess();
+}