Bug 123316 [Undo] - API BEHAVIOR - should always place a successfully undone/redone op on the redo/undo history
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
}
	/*
	 * Notify listeners that an operation is about to undo.
	 */
	private void notifyAboutToUndo(IUndoableOperation operation) {
		if (DEBUG_OPERATION_HISTORY_NOTIFICATION) {
			Tracing
					.printTrace("OPERATIONHISTORY", "ABOUT_TO_UNDO " 
							+ operation);
		}
		notifyListeners(new OperationHistoryEvent(
				OperationHistoryEvent.ABOUT_TO_UNDO, this, operation));
	}
	/*
	 * Notify listeners that an operation has been added.
	 */
	private void notifyAdd(IUndoableOperation operation) {
		if (DEBUG_OPERATION_HISTORY_NOTIFICATION) {
			Tracing.printTrace("OPERATIONHISTORY", "OPERATION_ADDED " 
					+ operation);
		}
		notifyListeners(new OperationHistoryEvent(
				OperationHistoryEvent.OPERATION_ADDED, this, operation));
	}
	/*
	 * Notify listeners that an operation is done executing.
	 */
	private void notifyDone(IUndoableOperation operation) {
		if (DEBUG_OPERATION_HISTORY_NOTIFICATION) {Tracing
			.printTrace("OPERATIONHISTORY", "DONE " + operation);