You might not have known but chrome can cast the entire desktop as well as just a tab. Or at least it can under windows, it works fine there. On macOS chrome the ...

As you may already know, Chromecast-enabled TVs and dongles, and other gadgets that support cast features can do so from Chrome on desktop computers as well as laptop and Chromebook platforms. More ...

Back in December, Google made official a YouTube app on the Cast-powered Chromecast that can be controlled by a remote on your phone, but a bug is causing desktop Chrome users to also see the new UI.