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
engine.applyStyles((Widget) widget, true);
				}
				public void style(Object widget) {
					engine.applyStyles((Widget) widget, true);
				}
				public CSSStyleDeclaration getStyle(Object widget) {
					Element e = engine.getCSSElementContext(widget)
							.getElement();
					if (e == null) {
						return null;
					}
					return engine.getViewCSS().getComputedStyle(e, null);
				}
				public void setClassnameAndId(Object widget, String classname,
						String id) {
					((Widget) widget).setData(
							"org.eclipse.e4.ui.css.CssClassName", classname); 
					((Widget) widget).setData("org.eclipse.e4.ui.css.id", id); 
					engine.applyStyles((Widget) widget, true);
				}
			});
			URL url;
			InputStream stream = null;
			try {
				url = FileLocator.resolve(new URL(cssURI));
				stream = url.openStream();
				engine.parseStyleSheet(stream);
			} catch (MalformedURLException e) {
				
				e.printStackTrace();