Wow, this is huge. People have been requesting this for a while.

This may be a redundant question, but does that mean the mobile app has support for it now too?

Yay finally ! Been waiting for this one

That's actually a system wide cast. When you do this it works great but the downside is that you are basically recording your screen and then sending it to Chromecast. Netflix, Plex, and other Chromecast apps do the proper route though and send meta information and sometimes authentication information to the Chromecast and then the Chromecast itself gets the raw compressed data stream and decodes it. Night and day difference if you have a 1080p mp4 video that you are casting via VLC with the built in option versus Plex/Netflix's native Chromecast solution.