It's called "App Runtime for Chrome".

http://chrome.blogspot.de/2014/09/fi...coming-to.html

http://arstechnica.com/gadgets/2014/...ting-required/ :

" ... The app code is all running on top of the Chrome platform, specifically inside of Native Client. In this way the ARC (App Runtime for Chrome) apps run in the same environment as other apps you can download from the Chrome Web Store, even though they are written on top of standard Android APIs.
...
There is no porting required. It seems that Google has built an entire Android stack into Chrome OS using Native Client. Both OSes are based on Linux, making libraries, the app framework, and the Android runtime the big differences. ..."