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
super.tearDown();
		applicationContext.dispose();
	}
	private IPresentationEngine getEngine() {
		if (engine == null) {
			IContributionFactory contributionFactory = (IContributionFactory) applicationContext
					.get(IContributionFactory.class.getName());
			Object newEngine = contributionFactory.create(getEngineURI(),
					applicationContext);
			assertTrue(newEngine instanceof IPresentationEngine);
			applicationContext.set(IPresentationEngine.class.getName(),
					newEngine);
			engine = (IPresentationEngine) newEngine;
		}
		return engine;
	}
	public void testFindPart_PartInWindow() {
		MApplication application = createApplication("partId");
		MWindow window = application.getChildren().get(0);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart part = partService.findPart("partId");
		assertNotNull(part);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		assertEquals(partStack.getChildren().get(0), part);
		part = partService.findPart("invalidPartId");
		assertNull(part);
	}
	public void testFindPart_PartNotInWindow() {