Bug 339573 Splitting the shared area with a part doesn't remove stale placeholders
The current code only looks for the addition of an MPlaceholder in the shared area as the hint to remove locals. When you split the area the element that gets added is the new MPartSashContainer...
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
protected IEventBroker eventBroker;
	@Inject
	EModelService modelService;
	@Inject
	protected Logger logger;
	private Shell limbo;
	private List<MUIElement> renderedElements = new ArrayList<MUIElement>();
	private MUIElement removeRoot = null;
	@Inject
	public PartRenderingEngine(
			@Named(E4Workbench.RENDERER_FACTORY_URI) @Optional String factoryUrl) {
		if (factoryUrl == null) {
			factoryUrl = defaultFactoryUrl;
		}
		this.factoryUrl = factoryUrl;
	}
	protected void fixZOrder(MUIElement element) {
		MElementContainer<MUIElement> parent = element.getParent();
		if (parent == null || !(element.getWidget() instanceof Control))
			return;
		Control elementCtrl = (Control) element.getWidget();
		Control prevCtrl = null;
		for (MUIElement kid : parent.getChildren()) {
			if (kid == element) {
				if (prevCtrl != null)
					elementCtrl.moveBelow(prevCtrl);
				else
					elementCtrl.moveAbove(null);
				return;
			} else if (kid.getWidget() instanceof Control) {