Bug 307747 EPartService doesn't render new parts
1. Have a part in a stack, it is the selected part. 2. Show another part in that stack using PartState.CREATE or PartState.VISIBLE. 3. The part should've been rendered. It is not.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public void testGetDirtyParts3_FalseTrue() {
		testGetDirtyParts3(false, true);
	}
	public void testGetDirtyParts3_FalseFalse() {
		testGetDirtyParts3(false, false);
	}
	public void testEvent_PartActivated() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = partStack.getChildren().get(0);
		MPart partBack = partStack.getChildren().get(1);
		partStack.setSelectedElement(partFront);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		assertEquals(partFront, partService.getActivePart());
		PartListener partListener = new PartListener();
		partService.addPartListener(partListener);
		partService.activate(partBack);
		assertEquals(1, partListener.getActivated());
		assertEquals(partBack, partListener.getActivatedParts().get(0));
		assertTrue(partListener.isValid());
	}
	public void testEvent_PartActivated2() {
		MApplication application = MApplicationFactory.eINSTANCE
				.createApplication();
		MWindow windowA = MApplicationFactory.eINSTANCE.createWindow();
		MWindow windowB = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(windowA);