Bug 148755 Add tthe status to the ActivityStackEvent.
If the the event rollback, the ActivityStackEvent status should be ROLL_BACK.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/activity/ActivityStack.java
* <p>
 * Notifications are sent as soon as a record is executed, even in the case of a
 * transaction. An alternative (more complex) implementation could provide an
 * additional hint to the UI that a transaction is in effect so that the UI can
 * batch up updates without repeating the same update unnecessarily. This
 * advanced mechanism would require some kind of "end update" event to be sent
 * to every listener that received a notification. Such a mechanism is beyond
 * the scope of this initial implementation, but can be added later if a proven
 * need arises.
 * <p>
 * Notifications are easiest to manage if each record affects a single element
 * called the target element. This is the element that will broadcast
 * notifications. The {@link AbstractElementRecord simple record}class
 * automates notifications for this case. More complex implementations are
 * possible, but the use of a transaction (or compound record) may be simpler in
 * many cases.
 * 
 * <h3>Scope of Change and Transactions</h3>
 * 
 * Each record affects a single element. However, many application-level
 * operations affect multiple elements. For example, an element may be
 * referenced by multiple elements. If the application wants to delete this
 * element, it must first remove the references, then do the deletion. Removing
 * references affects other elements, and so must be done as separate records.
 * Still, from the user perspective, the entire operation is an atomic
 * operation, to be undo and redone together. The solution is to use a
 * <em>compound record</em>. The compound record is undone and redone as
 * unit. The detailed operations are automatically performed in the proper
 * order.
 * <p>