I don't know about Chromium specifically, but in general Google requires 2 humans to have looked at every change (normally one is the author, but not necessarily for bot-authored changes).

They did roll this policy for Chromium changes a few years ago too.

And it wasn't just 2 humans but 2 Googlers. One Googler author and one Googler reviewer works. But an external author needed 2 Googlers to review changes, and all files needed to be reviewed by one author at least.

So if you touched multiple files owned by different people for a more complex feature, you would naturally get there.