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
window.getChildren().add(partB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		ClientEditor editorB = (ClientEditor) partB.getObject();
		assertFalse(editorB.wasFocusCalled());
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partB);
		assertTrue(editorB.wasFocusCalled());
	}
	public void testActivate_ChildWindow() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		window.getChildren().add(partA);
		window.setSelectedElement(partA);
		MWindow detachedWindow = BasicFactoryImpl.eINSTANCE.createWindow();
		window.getWindows().add(detachedWindow);
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		detachedWindow.getChildren().add(partB);
		detachedWindow.setSelectedElement(partB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partA);
		assertEquals(partA, partService.getActivePart());
		partService.activate(partB);
		assertEquals(partB, partService.getActivePart());