Bug 93400 LTK UI should provide official API for structural content in the preview page
org.eclipse.ltk.ui.refactoring/src/org/eclipse/ltk/internal/ui/refactoring/ChangeElementContentProvider.java
/* non Java-doc
	 * @see ITreeContentProvider#getParent
	 */
	public Object getParent(Object element){
		return ((ChangeElement)element).getParent();
	}
	
	/* non Java-doc
	 * @see ITreeContentProvider#hasChildren
	 */
	public boolean hasChildren(Object element){
		Object[] children= getChildren(element);
		return children != null && children.length > 0;
	}
	
	/* non Java-doc
	 * @see ITreeContentProvider#dispose
	 */
	public void dispose(){
	}
	
	/* non Java-doc
	 * @see ITreeContentProvider#getElements
	 */
	public Object[] getElements(Object element){
		return getChildren(element);
	}	
}