Simplify LoadableTextTrack construction

Source/core/html/track/InbandTextTrack.cpp

 /*
  * Copyright (C) 2012 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 23 matching lines @@
 #include <math.h>
 
 namespace WebCore {
 
 PassRefPtr<InbandTextTrack> InbandTextTrack::create(Document& document, TextTrackClient* client, PassRefPtr<InbandTextTrackPrivate> playerPrivate)
 {
     return adoptRef(new InbandTextTrack(document, client, playerPrivate));
 }
 
 InbandTextTrack::InbandTextTrack(Document& document, TextTrackClient* client, PassRefPtr<InbandTextTrackPrivate> tracksPrivate)
-    : TextTrack(document, client, emptyString(), tracksPrivate->label(), tracksPrivate->language(), InBand)
+    : TextTrack(document, client, emptyAtom, tracksPrivate->label(), tracksPrivate->language(), InBand)
     , m_private(tracksPrivate)
 {
     m_private->setClient(this);
 
     switch (m_private->kind()) {
     case InbandTextTrackPrivate::Subtitles:
         setKind(TextTrack::subtitlesKeyword());
         break;
     case InbandTextTrackPrivate::Captions:
         setKind(TextTrack::captionsKeyword());
@@ skipping 59 matching lines @@
     cue->setId(id);
     cue->setCueSettings(settings);
 
     if (hasCue(cue.get()))
         return;
 
     addCue(cue);
 }
 
 } // namespace WebCore