Bug 326177 EPartService's getActivePart() does not appear to work properly for an application with multiple windows
Based on the code in PartServiceCreationFunction, the EPartService implementation being returned when an application's context is queried seems to be a window-level EPartService implementation.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
assertNull(part);
		part = partService.findPart("partInWindow2");
		assertNotNull(part);
		partStack = (MPartStack) window2.getChildren().get(0);
		assertEquals(partStack.getChildren().get(0), part);
	}
	public void testBringToTop_PartOnTop() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = (MPart) partStack.getChildren().get(0);
		partStack.setSelectedElement(partFront);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.bringToTop(partFront);
		assertEquals(partStack.getSelectedElement(), partFront);
	}
	public void testBringToTop_PartOnTop_myService() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = (MPart) partStack.getChildren().get(0);
		partStack.setSelectedElement(partFront);
		getEngine().createGui(window);
		EPartService partService = (EPartService) partFront.getContext().get(
				EPartService.class.getName());
		partService.bringToTop(partFront);
		assertEquals(partStack.getSelectedElement(), partFront);
	}