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
}
	public void testEvent_PartHidden() {
		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);
		MPart partBack = (MPart) partStack.getChildren().get(1);
		partStack.setSelectedElement(partFront);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		assertEquals(partFront, partService.getActivePart());
		PartListener partListener = new PartListener();
		partService.addPartListener(partListener);
		partService.activate(partBack);
		assertEquals(1, partListener.getHidden());
		assertEquals(partFront, partListener.getHiddenParts().get(0));
		assertTrue(partListener.isValid());
		partListener.clear();
		partService.activate(partFront);
		assertEquals(1, partListener.getHidden());
		assertEquals(partBack, partListener.getHiddenParts().get(0));
		assertTrue(partListener.isValid());
	}
	public void testEvent_PartHidden2() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow windowA = BasicFactoryImpl.eINSTANCE.createWindow();
		MWindow windowB = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(windowA);