Add "change" and "removetrack" events to TextTrackList.

Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1191 matching lines @@
                 // If this is the first added track, create the list of text tracks.
                 if (!m_textTracks)
                     m_textTracks = TextTrackList::create(this);
             }
             break;
         }
     } else if (track->trackType() == TextTrack::AddTrack && track->mode() != TextTrack::disabledKeyword())
         textTrackAddCues(track, track->cues());
 
     configureTextTrackDisplay(AssumeVisibleChange);
+
+    ASSERT(textTracks()->contains(track));
+    textTracks()->scheduleChangeEvent();
 }
 
 void HTMLMediaElement::textTrackKindChanged(TextTrack* track)
 {
     if (track->kind() != TextTrack::captionsKeyword() && track->kind() != TextTrack::subtitlesKeyword() && track->mode() == TextTrack::showingKeyword())
         track->setMode(TextTrack::hiddenKeyword());
 }
 
 void HTMLMediaElement::beginIgnoringTrackDisplayUpdateRequests()
 {
@@ skipping 2661 matching lines @@
 {
     scheduleLayerUpdate();
 }
 
 bool HTMLMediaElement::isInteractiveContent() const
 {
     return fastHasAttribute(controlsAttr);
 }
 
 }