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#inputChanged
	 */
	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
		
	}
	
	/* non Java-doc
	 * @see ITreeContentProvider#getChildren
	 */
	public Object[] getChildren(Object o) {
		ChangeElement element= (ChangeElement)o;
		return element.getChildren();
	}