Bug 295611 [UI] The MPart tests leave many open shells
This turns out to be caused by the PRE's 'stop' method only working correctly when an MApplication is the 'uiRoot' element.
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/workbench/swt/internal/PartRenderingEngine.java
public static final String engineURI = "platform:/plugin/org.eclipse.e4.ui.workbench.swt/"
			+ "org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine";
	private String defaultRenderingFactoryId = "org.eclipse.e4.ui.workbench.renderers.default";
	private String curFactoryId = defaultRenderingFactoryId;
	IRendererFactory curFactory = null;
	
	private EventHandler visibilityHandler = new EventHandler() {
		public void handleEvent(Event event) {
			String attName = (String) event
					.getProperty(IUIEvents.EventTags.AttName);
			if (!IUIEvents.UIElement.Visible.equals(attName))
				return;
			MUIElement changedElement = (MUIElement) event
					.getProperty(IUIEvents.EventTags.Element);
			
			MElementContainer<?> parent = changedElement.getParent();
			AbstractPartRenderer parentFactory = parent != null ? getFactoryFor(parent)
					: null;
			if (parentFactory == null)
				return;
			if (changedElement.isVisible()) {
				Activator.trace(Policy.DEBUG_RENDERER, "visible -> true", null); 
				
				createGui(changedElement);
			} else {