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
EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA1);
		assertEquals(partA1, partService.getActivePart());
		MPart shownPart = partService.showPart("partB1",
				EPartService.PartState.VISIBLE);
		assertTrue(partService.isPartVisible(partA1));
		assertTrue(partService.isPartVisible(partB1));
		assertEquals(partA1, partService.getActivePart());
		assertEquals(partB1, shownPart);
		shownPart = partService.showPart("partB2",
				EPartService.PartState.VISIBLE);
		assertTrue(partService.isPartVisible(partA1));
		assertTrue(partService.isPartVisible(partB2));
		assertEquals(partA1, partService.getActivePart());
		assertEquals(partB2, shownPart);
	}
	public void testShowPart_Id_VISIBLE2() {
		MApplication application = MApplicationFactory.eINSTANCE
				.createApplication();
		MWindow window = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setId("partB");
		partDescriptor.setCategory("aCategory");
		application.getDescriptors().add(partDescriptor);
		MPartStack partStack = MApplicationFactory.eINSTANCE.createPartStack();
		partStack.setId("aCategory");
		window.getChildren().add(partStack);