Bug 337002 EPartService leaks previously active part
A reference is kept to the previously active part. This is unnecessary. We only need it to fire events. After the deactivation events have been fired, we should no longer need to keep it lying around.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
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);
	}
	public void testBringToTop_PartNotOnTop() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);