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
partSashContainer.setToBeRendered(false);
		window.getChildren().add(partSashContainer);
		MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();
		partStack.setToBeRendered(false);
		partSashContainer.getChildren().add(partStack);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		part.setElementId("partId");
		part.setToBeRendered(false);
		partStack.getChildren().add(part);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart shownPart = partService.showPart("partId", partState);
		assertEquals(1, partStack.getChildren().size());
		assertEquals(part, partStack.getChildren().get(0));
		assertEquals(part, shownPart);
		assertTrue("A shown part should be rendered", part.isToBeRendered());
	}
	public void testShowPart_Id_Unrendered_CREATE3() {
		testShowPart_Id_Unrendered3(PartState.CREATE);
	}
	public void testShowPart_Id_Unrendered_VISIBLE3() {
		testShowPart_Id_Unrendered3(PartState.VISIBLE);
	}
	public void testShowPart_Id_Unrendered_ACTIVATE3() {
		testShowPart_Id_Unrendered3(PartState.ACTIVATE);
	}
	private void testShowPart_Id_PartAlreadyShown(PartState partState) {
		MApplication application = createApplication(1, new String[1][0]);