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
partC.setCurSharedRef(placeholderC1);
		perspectiveA.getChildren().add(placeholderC1);
		perspectiveA.setSelectedElement(placeholderC1);
		
		MPerspective perspectiveB = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveB);
		MPlaceholder placeholderA2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderA2.setRef(partA);
		partA.setCurSharedRef(placeholderA2);
		perspectiveB.getChildren().add(placeholderA2);
		perspectiveB.setSelectedElement(placeholderA2);
		MPlaceholder placeholderB2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderB2.setRef(partB);
		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);