Bug 328946 Part activation history may return incorrect candidate if no placeholders could be found in a perspective
1. Window > Open Perspective > Other... > CVS Repository Exploring 2. Hide the 'CVS Repositories' view. 3. The 'History' view should become active, it is not.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MPart partFrontB = (MPart) partStackB.getChildren().get(0);
		MPart partBackB = (MPart) partStackB.getChildren().get(1);
		partStackB.setSelectedElement(partFrontB);
		getEngine().createGui(windowA);
		getEngine().createGui(windowB);
		EPartService partServiceA = (EPartService) partFrontA.getContext().get(
				EPartService.class.getName());
		EPartService partServiceB = (EPartService) partFrontB.getContext().get(
				EPartService.class.getName());
		partServiceA.bringToTop(partBackB);
		assertEquals(partStackA.getSelectedElement(), partFrontA);
		assertEquals(partStackB.getSelectedElement(), partFrontB);
		partServiceB.bringToTop(partBackA);
		assertEquals(partStackA.getSelectedElement(), partFrontA);
		assertEquals(partStackB.getSelectedElement(), partFrontB);
		partServiceA.bringToTop(partBackA);
		assertEquals(partStackA.getSelectedElement(), partBackA);
		assertEquals(partStackB.getSelectedElement(), partFrontB);
		partServiceB.bringToTop(partBackB);
		assertEquals(partStackA.getSelectedElement(), partBackA);
		assertEquals(partStackB.getSelectedElement(), partBackB);
	}
	/**
	 * Test to ensure that calling bringToTop(MPart) will change the active part
	 * if the active part is obscured by the part that's being brought to top.
	 */
	public void testBringToTop_ActivationChanges01() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();