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
public int getLimit(IUndoContext context) {
		if (!limits.containsKey(context)) {
			return DEFAULT_LIMIT;
		}
		return ((Integer) (limits.get(context))).intValue();
	}
	/*
	 * Consult the IOperationApprovers to see if the proposed redo should be
	 * allowed.
	 */
	private IStatus getRedoApproval(IUndoableOperation operation,
			IAdaptable info) {
		
		
		
		final IOperationApprover[] approverArray = (IOperationApprover[]) approvers
				.toArray(new IOperationApprover[approvers.size()]);
		for (int i = 0; i < approverArray.length; i++) {
			IOperationApprover approver = approverArray[i];
			IStatus approval = approver.proceedRedoing(operation, this, info);
			if (!approval.isOK()) {
				if (DEBUG_OPERATION_HISTORY_APPROVAL) {
					System.out
							.print("OPERATIONHISTORY >>> Redo not approved by ");  
					System.out.print(approver);
					System.out.print("for operation ");  
					System.out.print(operation);
					System.out.print(approval);
					System.out.println();
				}