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
extends ElementContainerItemProvider
	implements
		IEditingDomainItemProvider,
		IStructuredItemContentProvider,
		ITreeItemContentProvider,
		IItemLabelProvider,
		IItemPropertySource {
	/**
	 * This constructs an instance from a factory and a notifier.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	public WindowItemProvider(AdapterFactory adapterFactory) {
		super(adapterFactory);
	}
	/**
	 * This returns the property descriptors for the adapted class.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public List<IItemPropertyDescriptor> getPropertyDescriptors(Object object) {
		if (itemPropertyDescriptors == null) {
			super.getPropertyDescriptors(object);
			addLabelPropertyDescriptor(object);
			addIconURIPropertyDescriptor(object);
			addTooltipPropertyDescriptor(object);