Bug 327765 EPartService will hide a part of another perspective
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
private EModelService modelService;
	private LinkedList<MPart> generalActivationHistory = new LinkedList<MPart>();
	private Map<MUIElement, LinkedList<MPart>> perspectiveActivationHistories = new WeakHashMap<MUIElement, LinkedList<MPart>>();
	PartActivationHistory(EModelService modelService) {
		this.modelService = modelService;
	}
	public void clear() {
		generalActivationHistory.clear();
		perspectiveActivationHistories.clear();
	}
	void activate(MPart part, boolean activateBranch) {