Bug 88352 Operation supports leaks contexts via action handler
I20050315-1100 Susan, this is a different leak from the one that I reported. Test Case: 1. open text editor 2. close text editor ==> DefaultUndoManager is leaked due to undo/redo actions handlers still holding on to the context.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
preNotifyOperation(operation, event);
		for (int i = 0; i < listeners.size(); i++)
			try {
				((IOperationHistoryListener) listeners.get(i))
					.historyNotification(event);
			} catch (Exception e) {
				handleNotificationException(e);
			}
	}
	/*
	 * A history notification is about to be sent.  Notify the operation before hand
	 * if it implements IHistoryNotificationAwareOperation.
	 * 
	 * This method is provided for legacy undo frameworks that rely on notification
	 * from their undo managers before any listeners are notified about changes
	 * in the operation.
	 */
	private void preNotifyOperation(IUndoableOperation operation, OperationHistoryEvent event) {
		if (operation instanceof IHistoryNotificationAwareOperation) {
			try {
				((IHistoryNotificationAwareOperation)operation).aboutToNotify(event);
			} catch (Exception e) {
				handleNotificationException(e);
			}
		}
	}
	
	/*
	 * (non-Javadoc)
	 *