Bug 89031 [Undo/Redo] IWorkbench#getOperationSupport() marked experimental
IWorkbench#getOperationSupport() marked experimental
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/OperationHistoryFactory.java
* Return the operation history to be used for managing undoable operations.
	 * 
	 * @return the operation history to be used for executing, undoing, and
	 *         redoing operations.
	 */
	public static IOperationHistory getOperationHistory() {
		if (operationHistory == null) {
			operationHistory = new DefaultOperationHistory();
		}
		return operationHistory;
	}
	/**
	 * Set the operation history to be used for managing undoable operations.
	 * This method may only be called one time, and must be called before any 
	 * request to get the history.  Attempts to set the operation history will
	 * be ignored after it has been already set, or after a default one has 
	 * been created.
	 * 
	 * @param history -
	 *            the operation history to be used for executing, undoing, and
	 *            redoing operations.
	 */
	public static void setOperationHistory(IOperationHistory history) {
		
		if (operationHistory == null) {
			operationHistory = history;
		}
	}
}