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
MPartStack partStack = (MPartStack) window.getChildren().get(0);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		Collection<MPart> parts = partService.getParts();
		assertNotNull(parts);
		assertEquals(2, parts.size());
		assertTrue(parts.containsAll(partStack.getChildren()));
	}
	public void testGetParts_TwoWindows() {
		MApplication application = createApplication(new String[] { "partId",
				"partId2" }, new String[] { "partIA", "partIdB", "partIdC" });
		MWindow windowA = application.getChildren().get(0);
		MWindow windowB = application.getChildren().get(1);
		getEngine().createGui(windowA);
		getEngine().createGui(windowB);
		EPartService partServiceA = (EPartService) windowA.getContext().get(
				EPartService.class.getName());
		EPartService partServiceB = (EPartService) windowB.getContext().get(
				EPartService.class.getName());
		MPartStack partStackA = (MPartStack) windowA.getChildren().get(0);
		MPartStack partStackB = (MPartStack) windowB.getChildren().get(0);
		Collection<MPart> partsA = partServiceA.getParts();
		Collection<MPart> partsB = partServiceB.getParts();
		assertNotNull(partsA);
		assertEquals(2, partsA.size());
		assertTrue(partsA.containsAll(partStackA.getChildren()));
		assertNotNull(partsB);
		assertEquals(3, partsB.size());
		assertTrue(partsB.containsAll(partStackB.getChildren()));