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/src/org/eclipse/e4/ui/model/application/ui/basic/impl/BasicPackageImpl.java
* <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int TRIM_BAR__CHILDREN = UiPackageImpl.GENERIC_TRIM_CONTAINER__CHILDREN;
	/**
	 * The feature id for the '<em><b>Selected Element</b></em>' reference.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int TRIM_BAR__SELECTED_ELEMENT = UiPackageImpl.GENERIC_TRIM_CONTAINER__SELECTED_ELEMENT;
	/**
	 * The feature id for the '<em><b>Side</b></em>' attribute.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int TRIM_BAR__SIDE = UiPackageImpl.GENERIC_TRIM_CONTAINER__SIDE;
	/**
	 * The number of structural features of the '<em>Trim Bar</em>' class.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @generated
	 * @ordered
	 */
	public static final int TRIM_BAR_FEATURE_COUNT = UiPackageImpl.GENERIC_TRIM_CONTAINER_FEATURE_COUNT + 0;