Move HTMLLabelElement-related complexity out of Element

Source/core/html/HTMLLabelElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 29 matching lines @@
     virtual HTMLFormElement* formOwner() const OVERRIDE;
 
 private:
     explicit HTMLLabelElement(Document&);
     bool isInInteractiveContent(Node*) const;
 
     virtual bool rendererIsFocusable() const OVERRIDE;
     virtual bool isInteractiveContent() const OVERRIDE;
     virtual void accessKeyAction(bool sendMouseEvents) OVERRIDE;
 
+    virtual void attributeWillChange(const QualifiedName&, const AtomicString& oldValue, const AtomicString& newValue) OVERRIDE;
+    virtual InsertionNotificationRequest insertedInto(ContainerNode*) OVERRIDE;
+    virtual void removedFrom(ContainerNode*) OVERRIDE;
+
     // Overridden to update the hover/active state of the corresponding control.
     virtual void setActive(bool = true) OVERRIDE;
     virtual void setHovered(bool = true) OVERRIDE;
 
     // Overridden to either click() or focus() the corresponding control.
     virtual void defaultEventHandler(Event*) OVERRIDE;
 
     virtual void focus(bool restorePreviousSelection, FocusType) OVERRIDE;
+
+    void updateLabel(TreeScope&, const AtomicString& oldForAttributeValue, const AtomicString& newForAttributeValue);
 };
 
 } //namespace
 
 #endif