I'd rather have setMap call map.render. In this way the following still works:

```js
var map = new ol.Map({
  // ...
});
var control = new ol.control.ScaleLine({
  // ...
});
control.setMap(control);
```

The ability to add/remove controls to/from the map is a convenience – people who know what they're doing can get by without attaching controls to the map. By moving the call to render into setMap the limited responsibility of the addControl remains identical, it just adds the control to the map, and everything else is in setMap.

I hope my comments make sense.