Is there any downside for using a leading double slash to inherit the protocol in a URL? i.e. src="//domain.example"

I have a stylesheet that loads images from an external domain and I need it to load from https:// from secure order pages and http:// from other pages, based on the current URL. I found that starting the URL with a double slash inherits the current protocol. Do all browsers support this technique?

HTML ex:

<img src="//cdn.domain.example/logo.png" />

CSS ex:

.class { background: url(//cdn.domain.example/logo.png); }