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
* OPERATION_CHANGED indicates that an operation has changed in some way
	 * since it was added to the operations history.
	 * 
	 * (value is 6).
	 */
	public static final int OPERATION_CHANGED = 6;
	/**
	 * OPERATION_NOT_OK indicates that an operation was attempted and not
	 * successful. Listeners typically use this when they have prepared for an
	 * execute, undo, or redo, and need to know that the operation did not
	 * successfully complete. For example, listeners that turn redraw off before
	 * an operation is undone would turn redraw on when the operation completes,
	 * or when this notification is received, since there will be no
	 * notification of the completion.
	 * 
	 * (value is 7).
	 */
	public static final int OPERATION_NOT_OK = 7;
	/**
	 * OPERATION_REMOVED indicates an operation was removed from the history.
	 * Listeners typically remove any record of the operation that they may have
	 * kept in their own state. The operation has been disposed by the time
	 * listeners receive this notification.
	 * 
	 * (value is 8).
	 */
	public static final int OPERATION_REMOVED = 8;
	/**
	 * REDONE indicates that an operation was redone. Listeners can take
	 * appropriate action, such as revealing any relevant state in the UI.