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
MPart partB1 = BasicFactoryImpl.eINSTANCE.createPart();
		MPart partB2 = BasicFactoryImpl.eINSTANCE.createPart();
		partB1.setElementId("partB1");
		partB2.setElementId("partB2");
		partStackB.getChildren().add(partB1);
		partStackB.getChildren().add(partB2);
		partStackA.setSelectedElement(partA1);
		partStackB.setSelectedElement(partB1);
		window.setSelectedElement(partStackA);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA1);
		assertEquals(partA1, partService.getActivePart());
		MPart shownPart = partService.showPart("partB1",
				EPartService.PartState.VISIBLE);
		assertTrue(partService.isPartVisible(partA1));
		assertTrue(partService.isPartVisible(partB1));
		assertEquals(partA1, partService.getActivePart());
		assertEquals(partB1, shownPart);
		shownPart = partService.showPart("partB2",
				EPartService.PartState.VISIBLE);
		assertTrue(partService.isPartVisible(partA1));
		assertTrue(partService.isPartVisible(partB2));
		assertEquals(partA1, partService.getActivePart());
		assertEquals(partB2, shownPart);
	}
	public void testShowPart_Id_VISIBLE2() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE