Bug 324839 Secondary part selected by EPS due to initially selected part being hidden and removed does not get rendered
1. Have a stack with two parts in it, the selected one has been rendered, the other one is not. 2. Hide the selected part using the EPS. 3. The other part is now the selected part, but it is not rendered.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
public void testPartStack_SetActiveChildBug299379() throws Exception {
		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");
		partB.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		stack.getChildren().add(partA);
		stack.getChildren().add(partB);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		CTabFolder tabFolder = (CTabFolder) stack.getWidget();
		assertEquals(0, tabFolder.getSelectionIndex());
		EPartService service = (EPartService) window.getContext().get(
				EPartService.class.getName());
		service.activate(partB);
		assertEquals(
				"Activating another part should've altered the tab folder's selection",
				1, tabFolder.getSelectionIndex());
	}
	public void testPartStack_SetActiveChild2Bug299379() throws Exception {
		MApplication application = ApplicationFactoryImpl.eINSTANCE