Bug 317405 [Model] HandledItem should be abstract
Looks like an oversight the only real types are HandledMenuItem and HandledToolItem.
bundles/org.eclipse.e4.ui.model.workbench.edit/src/org/eclipse/e4/ui/model/application/ui/advanced/provider/PerspectiveStackItemProvider.java
(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MAdvancedFactory.INSTANCE.createPerspective()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MAdvancedFactory.INSTANCE.createPerspectiveStack()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MApplicationFactory.INSTANCE.createApplication()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MMenuFactory.INSTANCE.createHandledItem()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MMenuFactory.INSTANCE.createMenuSeparator()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MMenuFactory.INSTANCE.createMenu()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,
				 MMenuFactory.INSTANCE.createMenuContribution()));
		newChildDescriptors.add
			(createChildParameter
				(UiPackageImpl.Literals.ELEMENT_CONTAINER__CHILDREN,