You should just be able to use the same protocol-agnostic `//` approach that we use elsewhere.

```
<iframe width="960" height="540" src="//www.youtube.com/embed/cfiM87Y0pWw?rel=0&autoplay=1&enablejsapi=1&controls=0&showinfo=0&modestbranding=1" frameborder="0" allowfullscreen></iframe>
```