Google renewed its commitment to running Android apps on Chromebooks earlier this year with the announcement of universal Android app support going forward. One of the first devices covered by this promise is the Samsung Chromebook Plus, and it's also (apparently) the first to get the latest version of Android. Nougat (7.1.1) has started rolling out, but you need to be on the bleeding edge to get it.
Users of the Samsung Chromebook Plus are seeing the Nougat update from Marshmallow, but only if they're running the Canary build of Chrome. That's a step beyond running the dev channel as your device has to be in developer mode so you can enter some text commands. It's unstable, but you can apparently have Nougat right now.
Nougat on Chromebooks includes one big user-facing feature that will make Android apps much more usable—resizing. Yes, you'll have more choices than full screen and not full screen. There's no telling when this will end up in the dev channel, but hopefully soon. The Canary build is v60, so keep an eye out for that to hit the other channels.