Bug 323832 [UI] SashContainers are not being removed when unneeded
Start with a fresh workspace Drag the Problems view to the right of its current stack Drag it back... The problem is that the original drag created an MPartSashContainer to host the new stack but the drag back doesn't remove it (i.e. after dragging the Problems view back to its original stack there's now an MPSC with *only* the one stack in it).
bundles/org.eclipse.e4.ui.workbench.addons.swt/src/org/eclipse/e4/ui/workbench/addons/cleanupaddon/CleanupAddon.java
@Inject
	IEventBroker eventBroker;
	@Inject
	EModelService modelService;
	@Inject
	MApplication app;
	private EventHandler childrenHandler = new EventHandler() {
		public void handleEvent(Event event) {
			Object changedObj = event.getProperty(UIEvents.EventTags.ELEMENT);
			String eventType = (String) event.getProperty(UIEvents.EventTags.TYPE);
			if (UIEvents.EventTypes.REMOVE.equals(eventType)) {
				final MElementContainer<?> container = (MElementContainer<?>) changedObj;
				MUIElement containerParent = container.getParent();
				
				if (container instanceof MApplication || container instanceof MPerspectiveStack
						|| container instanceof MMenuElement || container instanceof MTrimBar) {
					return;
				}
				if (container instanceof MWindow && containerParent instanceof MApplication) {
					return;
				}
				Display display = Display.getCurrent();
				
				if (display != null) {
					Display.getCurrent().asyncExec(new Runnable() {
						public void run() {