It's somewhat unusual for Google to open source and mainline this bit of functionality. Last time I heard, Google's internal production Linux kernel still has 9000+ patches[0] on top of vanilla Linux. And I'm still waiting for them to open source switchto[1].

[0]: https://lwn.net/Articles/871195/

[1]: https://www.youtube.com/watch?v=KXuZi9aeGTw