Bug 326087 StackRenderer arbitrarily changes selected element when MPartStack is being unrendered
1. Open two files. 2. Activate the editor in the back. 3. Restart 4. The file in the wrong is active now. :O
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
window.setSelectedElement(stack);
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		EPartService partService = window.getContext().get(EPartService.class);
		MPlaceholder placeholderA = partService.createSharedPart("sharedA");
		stack.getChildren().add(placeholderA);
		stack.setSelectedElement(placeholderA);
		MPart partA = (MPart) placeholderA.getRef();
		assertNotNull(partA.getObject());
		stack.setToBeRendered(false);
		assertNull(partA.getObject());
	}
	public void testRemoveGuiBug324228_1() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		part.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		window.getSharedElements().add(part);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspectiveA = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveA.setElementId("perspectiveA");