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/BasicItemProviderAdapterFactory.java
* This sets the composed adapter factory that contains this factory.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	public void setParentAdapterFactory(ComposedAdapterFactory parentAdapterFactory) {
		this.parentAdapterFactory = parentAdapterFactory;
	}
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public boolean isFactoryForType(Object type) {
		return supportedTypes.contains(type) || super.isFactoryForType(type);
	}
	/**
	 * This implementation substitutes the factory itself as the key for the adapter.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 */
	@Override
	public Adapter adapt(Notifier notifier, Object type) {
		return super.adapt(notifier, this);
	}
	/**
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->