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
assertEquals(partB, partService.getActivePart());
		partService.hidePart(partB);
		assertEquals(partC, partService.getActivePart());
	}
	public void testHidePart_ActivationHistory_Bug328946_04() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart partC = BasicFactoryImpl.eINSTANCE.createPart();
		window.getSharedElements().add(partC);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspectiveA = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveA);
		perspectiveStack.setSelectedElement(perspectiveA);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		perspectiveA.getChildren().add(partA);
		perspectiveA.setSelectedElement(partA);
		MPerspective perspectiveB = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveB);
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		perspectiveB.getChildren().add(partB);
		perspectiveB.setSelectedElement(partB);
		MPlaceholder placeholderC = AdvancedFactoryImpl.eINSTANCE