Google has a long and interesting history contributing to the upstream
Linux kernel. With Chrome OS, Google has tried to learn from some of
the mistakes of its past and is now working with the upstream Linux kernel as
much as it can. In a session at the 2019
Open Source Summit North America , Google software engineer Doug
Anderson detailed how and why Chrome OS developers work upstream. It
is an effort intended to help the Linux community as well as Google.

Source: LWN.net – [$] How Chrome OS works upstream