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.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
stack.getChildren().add(partB);
		CTabItem item2 = folder.getItem(1);
		assertNull(
				"For a stack, the object will not be rendered unless explicitly required",
				item2.getControl());
		
		engine.createGui(partB);
		assertEquals(
				"The presentation engine should have created the part and set it",
				partB.getWidget(), item2.getControl());
		
		stack.setSelectedElement(partB);
		assertEquals("Selecting the element should not have changed anything",
				partB.getWidget(), item2.getControl());
	}
	public void testToBeRenderedCausesSelectionChanges() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
		window.getChildren().add(stack);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setElementId("partA");
		partA.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		partB.setElementId("partB");