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
partB.setCurSharedRef(placeholderB2);
		perspectiveB.getChildren().add(placeholderB2);
		MPlaceholder placeholderC2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderC2.setRef(partC);
		perspectiveB.getChildren().add(placeholderC2);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partC);
		perspectiveStack.setSelectedElement(perspectiveB);
		perspectiveB.getContext().activate();
		partService.activate(partA);
		partService.activate(partB);
		perspectiveStack.setSelectedElement(perspectiveA);
		perspectiveA.getContext().activate();
		partService.activate(partC);
		partService.hidePart(partC);
		perspectiveStack.setSelectedElement(perspectiveB);
		perspectiveB.getContext().activate();
		partService.hidePart(partB);
		assertEquals(partC, partService.getActivePart());
	}
	/**
	 * Tests that a perspective will automatically select another part as the
	 * active part after the originally active part that's being shown across
	 * multiple perspectives has been removed.
	 */
	public void testHidePart_ActivationHistory15() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE