Bug 317417 [Model] StackElement should be abstract and interface
StackElement is only a marker for improved containment hierarchies. We should at least make it abstract but also as an interface like WindowElement, ...
bundles/org.eclipse.e4.ui.model.workbench.edit/src/org/eclipse/e4/ui/model/application/ui/basic/provider/WindowItemProvider.java
MMenuFactory.INSTANCE.createRenderedMenu()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MMenuFactory.INSTANCE.createRenderedToolBar()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MMenuFactory.INSTANCE.createToolBarContribution()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MMenuFactory.INSTANCE.createTrimContribution()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MAdvancedFactory.INSTANCE.createPlaceholder()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MAdvancedFactory.INSTANCE.createPerspective()));
		newChildDescriptors.add
			(createChildParameter
				(BasicPackageImpl.Literals.WINDOW__SHARED_ELEMENTS,
				 MAdvancedFactory.INSTANCE.createPerspectiveStack()));
	}
	/**
	 * This returns the label text for {@link org.eclipse.emf.edit.command.CreateChildCommand}.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->