Add dummy dart:html library for documentation.

lib/html/doc/interface/TextTrackCue.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 TextTrackCue
+interface TextTrackCue extends EventTarget default _TextTrackCueFactoryProvider {
+
+  TextTrackCue(String id, num startTime, num endTime, String text, [String settings, bool pauseOnExit]);
+
+  /**
+   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
+   */
+  TextTrackCueEvents get on();
+
+  /** @domName TextTrackCue.align */
+  String align;
+
+  /** @domName TextTrackCue.endTime */
+  num endTime;
+
+  /** @domName TextTrackCue.id */
+  String id;
+
+  /** @domName TextTrackCue.line */
+  int line;
+
+  /** @domName TextTrackCue.pauseOnExit */
+  bool pauseOnExit;
+
+  /** @domName TextTrackCue.position */
+  int position;
+
+  /** @domName TextTrackCue.size */
+  int size;
+
+  /** @domName TextTrackCue.snapToLines */
+  bool snapToLines;
+
+  /** @domName TextTrackCue.startTime */
+  num startTime;
+
+  /** @domName TextTrackCue.text */
+  String text;
+
+  /** @domName TextTrackCue.track */
+  final TextTrack track;
+
+  /** @domName TextTrackCue.vertical */
+  String vertical;
+
+  /** @domName TextTrackCue.addEventListener */
+  void $dom_addEventListener(String type, EventListener listener, [bool useCapture]);
+
+  /** @domName TextTrackCue.dispatchEvent */
+  bool $dom_dispatchEvent(Event evt);
+
+  /** @domName TextTrackCue.getCueAsHTML */
+  DocumentFragment getCueAsHTML();
+
+  /** @domName TextTrackCue.removeEventListener */
+  void $dom_removeEventListener(String type, EventListener listener, [bool useCapture]);
+}
+
+interface TextTrackCueEvents extends Events {
+
+  EventListenerList get enter();
+
+  EventListenerList get exit();
+}