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
MPlaceholder areaPlaceholderB = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		areaPlaceholderB.setRef(area);
		perspectiveB.getChildren().add(areaPlaceholderB);
		perspectiveB.setSelectedElement(areaPlaceholderB);
		initialize(applicationContext, application);
		getEngine().createGui(window1);
		getEngine().createGui(window2);
		EPartService partService = window2.getContext().get(EPartService.class);
		partService.activate(sharedPart);
		partService.switchPerspective(perspectiveB);
		assertEquals(sharedPart, partService.getActivePart());
		partService.hidePart(sharedPart);
		assertNull(partService.getActivePart());
		application.setSelectedElement(window1);
		window1.getContext().activate();
		partService.switchPerspective(perspectiveA);
		assertEquals(window1.getContext(), application.getContext()
				.getActiveChild());
		assertEquals(perspectiveA.getContext(), window2.getContext()
				.getActiveChild());
	}
	/**
	 * Test to ensure that the method annotated with the {@link Focus}
	 * annotation is invoked when switching between perspectives.
	 */
	public void testSwitchPerspective06() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();