Introduce "navigation target classification" for spatial navigation

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003-2011, 2013, 2014 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
@@ skipping 503 matching lines @@
     virtual void removedFrom(ContainerNode*) override;
     virtual void childrenChanged(const ChildrenChange&) override;
 
     virtual void willRecalcStyle(StyleRecalcChange);
     virtual void didRecalcStyle(StyleRecalcChange);
     virtual PassRefPtr<RenderStyle> customStyleForRenderer();
 
     virtual bool shouldRegisterAsNamedItem() const { return false; }
     virtual bool shouldRegisterAsExtraNamedItem() const { return false; }
 
-    bool supportsSpatialNavigationFocus() const;
-
     void clearTabIndexExplicitlyIfNeeded();
     void setTabIndexExplicitly(short);
     // Subclasses may override this method to affect focusability. Unlike
     // supportsFocus, this method must be called on an up-to-date layout, so it
     // may use the renderer to reason about focusability. This method cannot be
     // moved to RenderObject because some focusable nodes don't have renderers,
     // e.g., HTMLOptionElement.
     virtual bool rendererIsFocusable() const;
 
     // classAttributeChanged() exists to share code between
@@ skipping 344 matching lines @@
     static PassRefPtrWillBeRawPtr<T> create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     PassRefPtrWillBeRawPtr<T> T::create(const QualifiedName& tagName, Document& document) \
     { \
         return adoptRefWillBeNoop(new T(tagName, document)); \
     }
 
 } // namespace
 
 #endif // Element_h