Bug 313407 EPartService needs to use EModelService's bringToTop method
The EMS variant considers shared parts, the EPS should delegate accordingly.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/workbench/ui/internal/PartServiceImpl.java
case ACTIVATE:
			activate(part);
			return part;
		case VISIBLE:
			MPart activePart = getActivePart();
			if (activePart == null) {
				bringToTop(part);
			} else if (activePart.getParent() == part.getParent()) {
				
				part.setToBeRendered(true);
				engine.createGui(part);
			} else {
				bringToTop(part);
			}
			return part;
		case CREATE:
			part.setToBeRendered(true);
			engine.createGui(part);
			return part;
		}
		return part;
	}
	public MPart showPart(String id, PartState partState) {
		Assert.isNotNull(id);
		Assert.isNotNull(partState);
		MPart part = findPart(id);
		if (part != null) {
			return showPart(part, partState);
		}
		MPartDescriptor descriptor = findDescriptor(id);