Bug 336225 Trim bars do not get unrendered by the rendering engine when trimmed window is unrendered
The trim bars are "ignored" by the rendering engine as it does not perform an unrendering pass on them when the parent trimmed window is being unrendered.
bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/PartRenderingEngine.java
/**
	 * Initialize a part renderer from the extension point.
	 * 
	 * @param context
	 *            the context for the part factories
	 */
	@PostConstruct
	void initialize(IEclipseContext context) {
		this.appContext = context;
		
		KeyFormatterFactory.setDefault(SWTKeySupport
				.getKeyFormatterForPlatform());
		
		context.set(IPresentationEngine.class.getName(), this);
		IRendererFactory factory = null;
		IContributionFactory contribFactory = context
				.get(IContributionFactory.class);
		try {
			factory = (IRendererFactory) contribFactory.create(factoryUrl,
					context);
		} catch (Exception e) {
			logger.warn(e, "Could not create rendering factory");
		}
		
		if (factory == null) {
			try {
				factory = (IRendererFactory) contribFactory.create(
						defaultFactoryUrl, context);
			} catch (Exception e) {
				logger.error(e, "Could not create default rendering factory");