Remove Apple's unused implementation of private browsing from WebCore

Source/WebCore/html/HTMLMediaElement.h

 /*
  * 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 279 matching lines @@
 
     bool hasClosedCaptions() const;
     bool closedCaptionsVisible() const;
     void setClosedCaptionsVisible(bool);
 
     MediaControls* mediaControls() const;
 
     void sourceWasRemoved(HTMLSourceElement*);
     void sourceWasAdded(HTMLSourceElement*);
 
-    void privateBrowsingStateDidChange();
-
     // Media cache management.
     static void getSitesInMediaCache(Vector<String>&);
     static void clearMediaCache();
     static void clearMediaCacheForSite(const String&);
     static void resetMediaEngines();
 
     bool isPlaying() const { return m_playing; }
 
     virtual bool hasPendingActivity() const;
 
@@ skipping 398 matching lines @@
 inline HTMLMediaElement* toMediaElement(Node* node)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!node || isMediaElement(node));
     return static_cast<HTMLMediaElement*>(node);
 }
 
 } //namespace
 
 #endif
 #endif