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/ChangeElement.java
* 
	 * @return the change or <code>null</code>
	 */
	public abstract Change getChange();
	
	/**
	 * Sets the activation status for this <code>ChangeElement</code>. When a 
	 * change element is not active,  then executing it is expected to do nothing.
	 *
	 * @param enabled the activation status for this change element
	 */
	public abstract void setEnabled(boolean enabled);
	
	/**
	 * Sets the activation status for this <code>ChangeElement</code>. When a 
	 * change element is not active,  then executing it is expected to do nothing.
	 *
	 * @param enabled the activation status for this change element
	 */
	public abstract void setEnabledShallow(boolean enabled);
	
	/**
	 * Returns the activation status of this <code>ChangeElement</code>.
	 * Returns one of the following values: <code>IChange.ACTIVE</code>
	 * if the node and all its children are active, <code>IChange.INACTIVE</code>
	 * if all children and the node itself is inactive, and <code>IChange.PARTLY_ACTIVE
	 * </code>otherwise.
	 *
	 * @return the change element's activation status.
	 */