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/IOperationHistory.java
*            user if necessary. When this parameter is not <code>null</code>,
	 *            it should minimally contain an adapter for the
	 *            org.eclipse.swt.widgets.Shell.class.
	 * 
	 * @return the IStatus indicating whether the redo succeeded.
	 * 
	 * <p>
	 * The severity code in the returned status describes whether the operation
	 * succeeded and whether it remains in the history. <code>OK</code>
	 * severity indicates that the redo operation was successful. The operation
	 * will be placed on the undo history, provided it can be undone (answers
	 * <code>true</code> to {@link IUndoableOperation#canUndo()}). Listeners
	 * will receive the <code>REDONE</code> notification.
	 * </p>
	 * <p>
	 * Other severity codes (<code>CANCEL</code>, <code>ERROR</code>,
	 * <code>INFO</code>, etc.) are not specifically interpreted by the
	 * history. The operation will remain in the history and the returned status
	 * is simply passed back to the caller. For all severities other than <code>OK</code>,
	 * listeners will receive the <code>OPERATION_NOT_OK</code> notification
	 * instead of the <code>REDONE</code> notification if the redo was
	 * approved and attempted.
	 * </p>
	 * 
	 * @throws ExecutionException
	 *             if an exception occurred during redo.
	 */
	IStatus redoOperation(IUndoableOperation operation,
			IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException;