Bug 105697 [Undo] - OperationHistoryEvent - cannot distinguish between canceled event or failed event
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
OperationHistoryEvent.ABOUT_TO_EXECUTE, this, operation));
	}
	/*
	 * Notify listeners that an operation is about to redo.
	 */
	private void notifyAboutToRedo(IUndoableOperation operation) {
		if (DEBUG_OPERATION_HISTORY_NOTIFICATION) {
			System.out.print("OPERATIONHISTORY >>> ABOUT_TO_REDO ");  
			System.out.print(operation);
			System.out.println();
		}
		notifyListeners(new OperationHistoryEvent(
				OperationHistoryEvent.ABOUT_TO_REDO, this, operation));
	}
	/*
	 * Notify listeners that an operation is about to undo.
	 */
	private void notifyAboutToUndo(IUndoableOperation operation) {
		if (DEBUG_OPERATION_HISTORY_NOTIFICATION) {
			System.out.print("OPERATIONHISTORY >>> ABOUT_TO_UNDO ");  
			System.out.print(operation);
			System.out.println();
		}
		notifyListeners(new OperationHistoryEvent(
				OperationHistoryEvent.ABOUT_TO_UNDO, this, operation));
	}
	/*
	 * Notify listeners that an operation has been added.
	 */
	private void notifyAdd(IUndoableOperation operation) {