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
assertEquals(1, stack.getChildren().size());
		assertEquals(part, stack.getChildren().get(0));
		assertEquals(part, partService.getActivePart());
	}
	public void testShowPart_Id_VISIBLE() {
		MApplication application = MApplicationFactory.eINSTANCE
				.createApplication();
		MWindow window = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartStack partStackA = MApplicationFactory.eINSTANCE.createPartStack();
		MPartStack partStackB = MApplicationFactory.eINSTANCE.createPartStack();
		window.getChildren().add(partStackA);
		window.getChildren().add(partStackB);
		MPart partA1 = MApplicationFactory.eINSTANCE.createPart();
		MPart partA2 = MApplicationFactory.eINSTANCE.createPart();
		partA1.setId("partA1");
		partA2.setId("partA2");
		partStackA.getChildren().add(partA1);
		partStackA.getChildren().add(partA2);
		MPart partB1 = MApplicationFactory.eINSTANCE.createPart();
		MPart partB2 = MApplicationFactory.eINSTANCE.createPart();
		partB1.setId("partB1");
		partB2.setId("partB2");
		partStackB.getChildren().add(partB1);
		partStackB.getChildren().add(partB2);
		partStackA.setSelectedElement(partA1);
		partStackB.setSelectedElement(partB1);
		window.setSelectedElement(partStackA);
		initialize(applicationContext, application);
		getEngine().createGui(window);