Bug 105697 [Undo] - OperationHistoryEvent - cannot distinguish between canceled event or failed event
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/OperationHistoryEvent.java
* Listeners should prepare for the undo as appropriate. Listeners will
	 * receive an UNDONE notification if the operation is successful, or an
	 * OPERATION_NOT_OK notification if the undo is cancelled or otherwise
	 * fails.
	 * 
	 * (value is 3).
	 */
	public static final int ABOUT_TO_UNDO = 3;
	/**
	 * DONE indicates that an operation has been executed. Listeners can take
	 * appropriate action, such as revealing any relevant state in the UI. This
	 * notification is only received for those operations executed by the
	 * operation history. Operations that are added to the history after
	 * execution do not trigger this notification.
	 * 
	 * Clients will also receive a notification that the operation has been
	 * added to the history.
	 * 
	 * (value is 4).
	 */
	public static final int DONE = 4;
	/**
	 * OPERATION_ADDED indicates that an operation was added to the history.
	 * Listeners can use this notification to add their undo context to a new operation as
	 * appropriate or otherwise record the operation.
	 * 
	 * (value is 5).
	 */
	public static final int OPERATION_ADDED = 5;
	/**