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
* record history. Records are defined to always work. That is, when a record is
 * told to execute, undo or redo, the record operation must succeed. If there
 * are issues that might prevent the execution from succeeding, they must be
 * checked by the application <em>before</em> issuing the record. If a record
 * returns true from canUndo( ), then it must successfully undo, assuming that
 * the state of the model is correct. Similarly, if a record returns true from
 * canRedo( ), then the redo must succeed, again assuming the model state is
 * valid. The only way the model state could be invalid is due to a programming
 * error, and so asserts should be used to verify that the state is valid.
 * Another way of saying this is that records <em>cannot</em> throw
 * application-level exceptions: they must succeed. Any exceptions thrown would
 * be system-level exceptions such as null- pointer violations, out-of-memory
 * errors and other generic problems.
 * 
 * <h3>Persistence Support</h3>
 * 
 * The record stack contains a dirty property. This property can be used to
 * determine when persisting the Records' changes is required. Upon
 * construction, the undo stack is empty, and is not dirty.
 * 
 * <h3>Dirty State Support</h3>
 * 
 * A design is considered <em>dirty</em> if the in-memory state differs from
 * that on disk. There are three primary considerations:
 * <p>
 * <ul>
 * <li>The user has made changes to the file since it was loaded or saved. The
 * file is considered dirty.</li>
 * <li>The user has made changes, then undone them so that the file is back to
 * the same state as on disk. In this case, the file is <em>not</em> dirty.