Bug 249574 [Contributions] ExternalActionManager.addPropertyChangeListener() doesn't register the ListenerList
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ExternalActionManager.java
* 			The action contribution that caused the exception,
		 * 			never <code>null</code>.
		 * @param exception
		 * 			The <code>ExecutionException</code>, never <code>null</code>.
		 */
		public void postExecuteFailure(IAction action,
				ExecutionException exception);
	}
	/**
	 * A callback mechanism for some external tool to communicate extra
	 * information to actions and action contribution items.
	 * 
	 * @since 3.0
	 */
	public static interface ICallback {
		/**
		 * <p>
		 * Adds a listener to the object referenced by <code>identifier</code>.
		 * This listener will be notified if a property of the item is to be
		 * changed. This identifier is specific to mechanism being used. In the
		 * case of the Eclipse workbench, this is the command identifier.
		 * </p>
		 * <p>
		 * Has no effect if an identical listener has already been added for
		 * the <code>identifier</code>.
		 * </p>
		 * 
		 * @param identifier
		 *            The identifier of the item to which the listener should be
		 *            attached; must not be <code>null</code>.