Prevent 'removetrack' events from firing when all inband text tracks are removed.

Source/core/html/track/TextTrack.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  * Copyright (C) 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 128 matching lines @@
     if (value == descriptionsKeyword())
         return true;
     if (value == chaptersKeyword())
         return true;
     if (value == metadataKeyword())
         return true;
 
     return false;
 }
 
+void TextTrack::setTrackList(TextTrackList* trackList)
+{
+    m_trackList = trackList;
+    if (!m_trackList && m_cues && m_client)
+        m_client->textTrackRemoveCues(this, m_cues.get());
+}
+
 void TextTrack::setKind(const AtomicString& newKind)
 {
     AtomicString oldKind = kind();
     TrackBase::setKind(newKind);
 
     if (m_client && oldKind != kind())
         m_client->textTrackKindChanged(this);
 }
 
 void TextTrack::setMode(const AtomicString& mode)
@@ skipping 257 matching lines @@
 {
     return EventTargetNames::TextTrack;
 }
 
 ExecutionContext* TextTrack::executionContext() const
 {
     return m_document;
 }
 
 } // namespace WebCore
-