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
org.eclipse.swt.widgets.Listener keyListener;
	
	private EventHandler toBeRenderedHandler = new EventHandler() {
		public void handleEvent(Event event) {
			MUIElement changedElement = (MUIElement) event
					.getProperty(UIEvents.EventTags.ELEMENT);
			MElementContainer<?> parent = changedElement.getParent();
			
			if (parent == null && changedElement instanceof MWindow) {
				parent = (MElementContainer<?>) ((EObject) changedElement)
						.eContainer();
			}
			boolean menuChild = parent instanceof MMenu;
			
			if (!(parent instanceof MApplication)
					&& (parent == null || parent.getWidget() == null || menuChild))
				return;
			if (changedElement.isToBeRendered()) {
				Activator.trace(Policy.DEBUG_RENDERER, "visible -> true", null); 
				
				Object w = createGui(changedElement);
				if (w instanceof Control && !(w instanceof Shell)) {
					fixZOrder(changedElement);
				}
			} else {
				Activator
						.trace(Policy.DEBUG_RENDERER, "visible -> false", null); 
				
				
				if (parent.getSelectedElement() == changedElement)