The following seems to keep Chrome from re-downloading this beast:

    # From one's $HOME dir:
    rm -fr ./.config/google-chrome/OptGuideOnDeviceModel
    mkdir -p ./.config/google-chrome/OptGuideOnDeviceModel
    touch ./.config/google-chrome/OptGuideOnDeviceModel/weights.bin
    chmod 0400 ./.config/google-chrome/OptGuideOnDeviceModel/weights.bin
    chmod 0500 ./.config/google-chrome/OptGuideOnDeviceModel
Adapt as appropriate for your OS. For "Chrome Unstable" installs, the dir name is google-chrome-unstable.

This has, so far, kept Chrome from (re)installing that file on my system.

Hypothetically the parts involving weights.bin aren't needed so long as the containing directory is not writable.

FYI, this doesn't appear to work on macOS, unless I'm lucky enough that Chrome has never installed anything related to this on my machine. I don't even have a ~/.config/google-chrome directory; it's possible Google is using some Apple-alternative to that standard.