It's embedded CEF, fyi. And I'm fairly certain the new friends UI (which is built using a web stack) isn't Electron, but still just leveraging their existing CEF implementation.
Valve also use HTML/CSS (or some form of it) for their game UIs using Panorama, but this doesn't use any form of web browser from my knowledge.
Valve also use HTML/CSS (or some form of it) for their game UIs using Panorama, but this doesn't use any form of web browser from my knowledge.