Bug 249574 [Contributions] ExternalActionManager.addPropertyChangeListener() doesn't register the ListenerList
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ExternalActionManager.java
* @param commandManager
		 *            The command manager which will provide the callback; must
		 *            not be <code>null</code>.
		 * @param activeChecker
		 *            The callback mechanism for checking whether a command is
		 *            active; must not be <code>null</code>.
		 * 
		 * @since 3.1
		 */
		public CommandCallback(final BindingManager bindingManager,
				final CommandManager commandManager,
				final IActiveChecker activeChecker) {
			this(bindingManager, commandManager, activeChecker,
					new IExecuteApplicable() {
				public boolean isApplicable(IAction action) {
					return true;
				}
			});
		}
		/**
		 * Constructs a new instance of <code>CommandCallback</code> with the
		 * workbench it should be using.
		 * 
		 * @param bindingManager
		 *            The binding manager which will provide the callback; must
		 *            not be <code>null</code>.
		 * @param commandManager
		 *            The command manager which will provide the callback; must
		 *            not be <code>null</code>.
		 * @param activeChecker