Apple - How to sync passwords between Chrome and iCloud Keychain
I found this:
You can no longer share Google Chrome passwords with iCloud Keychain. Google Chrome 45 was the last one that could do it. Since then its been removed as an option.
Perhaps reaching out to Google Support and giving them something to pass on to the devs for Chrome for Mac could inspire something.
Until they replace it, I recommend using a 3rd Party option since they work with nearly every platform and device type. Such as LastPass, Dashlane, Roboform, Keepass, 1Password, Privacy, GNOME keyring, etc.
They may work with Keychain and gather passwords saved in Chrome. Thats the only auto-sync solution that is available.