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
application.getChildren().add(window);
		application.setSelectedElement(window);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setCategory("categoryId");
		partDescriptor.setId("partId");
		application.getDescriptors().add(partDescriptor);
		partDescriptor = MApplicationFactory.eINSTANCE.createPartDescriptor();
		partDescriptor.setCategory("categoryId");
		partDescriptor.setId("partId2");
		application.getDescriptors().add(partDescriptor);
		MPartStack stack = MApplicationFactory.eINSTANCE.createPartStack();
		stack.getTags().add("categoryId");
		window.getChildren().add(stack);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart part = partService.showPart("partId", PartState.ACTIVATE);
		assertEquals(1, stack.getChildren().size());
		assertEquals(part, stack.getChildren().get(0));
		assertEquals(part, stack.getSelectedElement());
		MPart part2 = partService.showPart("partId2", PartState.ACTIVATE);
		assertEquals(2, stack.getChildren().size());
		assertEquals(part, stack.getChildren().get(0));
		assertEquals(part2, stack.getChildren().get(1));
		assertEquals(part2, stack.getSelectedElement());
	}
	public void testShowPart_Id_CREATE() {
		MApplication application = MApplicationFactory.eINSTANCE