Get rid of extraneous accessibility tree traversal code.

Source/core/accessibility/AccessibilityRenderObject.h

 /*
  * Copyright (C) 2008 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
@@ skipping 151 matching lines @@
     // Hit testing.
     virtual AccessibilityObject* accessibilityHitTest(const IntPoint&) const;
     virtual AccessibilityObject* elementAccessibilityHitTest(const IntPoint&) const;
 
     // High-level accessibility tree access. Other modules should only use these functions.
     virtual AccessibilityObject* parentObject() const;
     virtual AccessibilityObject* parentObjectIfExists() const;
 
     // Low-level accessibility tree exploration, only for use within the accessibility module.
     virtual AccessibilityObject* firstChild() const;
-    virtual AccessibilityObject* lastChild() const;
-    virtual AccessibilityObject* previousSibling() const;
     virtual AccessibilityObject* nextSibling() const;
     virtual void addChildren();
     virtual bool canHaveChildren() const;
     virtual void updateChildrenIfNecessary();
     virtual void setNeedsToUpdateChildren() { m_childrenDirty = true; }
     virtual void clearChildren();
     virtual AccessibilityObject* observableObject() const;
 
     // Properties of the object's owning document or page.
     virtual double estimatedLoadingProgress() const;
@@ skipping 71 matching lines @@
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isAccessibilityRenderObject());
     return static_cast<const AccessibilityRenderObject*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toAccessibilityRenderObject(const AccessibilityRenderObject*);
 
 } // namespace WebCore
 
 #endif // AccessibilityRenderObject_h