Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/TextTrack.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 TextTrack
-interface TextTrack extends EventTarget {
-
-  /**
-   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
-   */
-  TextTrackEvents get on();
-
-  static final int DISABLED = 0;
-
-  static final int HIDDEN = 1;
-
-  static final int SHOWING = 2;
-
-  /** @domName TextTrack.activeCues */
-  final TextTrackCueList activeCues;
-
-  /** @domName TextTrack.cues */
-  final TextTrackCueList cues;
-
-  /** @domName TextTrack.kind */
-  final String kind;
-
-  /** @domName TextTrack.label */
-  final String label;
-
-  /** @domName TextTrack.language */
-  final String language;
-
-  /** @domName TextTrack.mode */
-  int mode;
-
-  /** @domName TextTrack.addCue */
-  void addCue(TextTrackCue cue);
-
-  /** @domName TextTrack.addEventListener */
-  void $dom_addEventListener(String type, EventListener listener, [bool useCapture]);
-
-  /** @domName TextTrack.dispatchEvent */
-  bool $dom_dispatchEvent(Event evt);
-
-  /** @domName TextTrack.removeCue */
-  void removeCue(TextTrackCue cue);
-
-  /** @domName TextTrack.removeEventListener */
-  void $dom_removeEventListener(String type, EventListener listener, [bool useCapture]);
-}
-
-interface TextTrackEvents extends Events {
-
-  EventListenerList get cueChange();
-}