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
MPartStack partStackB = BasicFactoryImpl.eINSTANCE.createPartStack();
		perspective.getChildren().add(partStackB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		MPlaceholder placeholderB = partService
				.createSharedPart("partId", true);
		MPart partB = (MPart) placeholderB.getRef();
		partB.setCurSharedRef(placeholderB);
		placeholderB.setToBeRendered(false);
		partB.setToBeRendered(false);
		partStackB.getChildren().add(placeholderB);
		partStackB.setSelectedElement(null);
		partService.showPart(partB, PartState.VISIBLE);
		assertNotNull(partStackB.getSelectedElement());
		assertEquals(placeholderB, partStackB.getSelectedElement());
	}
	public void testShowPart_Bug322403_C() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspective = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspective);