UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.76 Safari/537.36

Steps to reproduce the problem:
See http://www.brynosaurus.com/cachedir/spec.html
Adopting such "standard" would help a lot people doing full-system backups of their desktop hosts, where browser cache might have a relevant size and definitely doesn't need backup.

What is the expected behavior?
a CACHEDIR.TAG file (with the appropriate content) to be present in ~/.cache/chromium/ and ~/.config/chromium/Default/Application Cache/, and all other relevant cache directories.

What went wrong?
.

Did this work before? N/A 

Chrome version: 56.0.2924.76  Channel: n/a
OS Version: 
Flash Version: