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
MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setAllowMultiple(multipleAllowed);
		partDescriptor.setElementId("partId");
		application.getDescriptors().add(partDescriptor);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart createdPart = partService.createPart("partId");
		MPart shownPart = partService.showPart(createdPart, partState);
		assertNotNull(shownPart);
		assertEquals(createdPart, shownPart);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueACTIVATE() {
		testShowPart_Part_MultipleNonexistent(true, PartState.ACTIVATE);
	}
	public void testShowPart_Part_MultipleNonexistent_FalseACTIVATE() {
		testShowPart_Part_MultipleNonexistent(false, PartState.ACTIVATE);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueVISIBLE() {
		testShowPart_Part_MultipleNonexistent(true, PartState.VISIBLE);
	}
	public void testShowPart_Part_MultipleNonexistent_FalseVISIBLE() {
		testShowPart_Part_MultipleNonexistent(false, PartState.VISIBLE);
	}
	public void testShowPart_Part_MultipleNonexistent_TrueCREATE() {