Stop pushing the value of 'default' to LoadableTextTrack

Source/core/html/track/LoadableTextTrack.h

 /*
  * Copyright (C) 2011 Google 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 37 matching lines @@
 
     // TextTrack method.
     virtual void setMode(const AtomicString&) override;
 
     size_t trackElementIndex();
     HTMLTrackElement* trackElement() { return m_trackElement; }
 #if !ENABLE(OILPAN)
     void clearTrackElement();
 #endif
 
-    virtual bool isDefault() const override { return m_isDefault; }
-    virtual void setIsDefault(bool isDefault) override  { m_isDefault = isDefault; }
+    virtual bool isDefault() const override;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     // TextTrackLoaderClient
     virtual void newCuesAvailable(TextTrackLoader*) override;
     virtual void cueLoadingCompleted(TextTrackLoader*, bool loadingFailed) override;
     virtual void newRegionsAvailable(TextTrackLoader*) override;
 
     explicit LoadableTextTrack(HTMLTrackElement*);
 
     void loadTimerFired(Timer<LoadableTextTrack>*);
 
     RawPtrWillBeMember<HTMLTrackElement> m_trackElement;
     Timer<LoadableTextTrack> m_loadTimer;
     OwnPtrWillBeMember<TextTrackLoader> m_loader;
     KURL m_url;
-    bool m_isDefault;
 };
 } // namespace blink
 
 #endif