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
MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();
		sharedSashContainer.getChildren().add(partStack);
		sharedSashContainer.setSelectedElement(partStack);
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		assertNotNull(partStack.getWidget());
		assertNotNull(sharedSashContainer.getWidget());
		assertNotNull(sashContainer.getWidget());
	}
	private MWindow createWindowWithOneView(String partName) {
		final MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		window.setHeight(300);
		window.setWidth(400);
		window.setLabel("MyWindow");
		MPartSashContainer sash = BasicFactoryImpl.eINSTANCE
				.createPartSashContainer();
		window.getChildren().add(sash);
		MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
		sash.getChildren().add(stack);
		MPart contributedPart = BasicFactoryImpl.eINSTANCE.createPart();
		stack.getChildren().add(contributedPart);
		contributedPart.setLabel(partName);
		contributedPart
				.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		return window;
	}
}