Bug 249574 [Contributions] ExternalActionManager.addPropertyChangeListener() doesn't register the ListenerList
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ExternalActionManager.java
/**
		 * @since 3.4
		 */
		public void notDefined(IAction action, NotDefinedException exception) {
			String actionDefinitionId = action.getActionDefinitionId();
			if (actionDefinitionId==null 
					|| !applicabilityChecker.isApplicable(action)) {
				return;
			}
			commandManager.fireNotDefined(actionDefinitionId, exception);
		}
		/**
		 * @since 3.4
		 */
		public void notEnabled(IAction action, NotEnabledException exception) {
			String actionDefinitionId = action.getActionDefinitionId();
			if (actionDefinitionId==null 
					|| !applicabilityChecker.isApplicable(action)) {
				return;
			}
			commandManager.fireNotEnabled(actionDefinitionId, exception);
		}
	}
	/**
	 * Defines a callback mechanism for developer who wish to further control
	 * the visibility of legacy action-based contribution items.
	 * 
	 * @since 3.1
	 */
	public static interface IActiveChecker {