UserAgent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0

Steps to reproduce the problem:
1. Try to sort Tibetan in JavaScript in Chrome with Intl.Collator
2. Observe that the result of Intl.Collator.supportedLocalesOf(['dz', 'bo', 'dz-BU', 'bo-IN']) is the empty String
3. Look at possible locales on https://developer.chrome.com/webstore/i18n#localeTable
4. see that "Tibetan" is not among these
5. sigh

What is the expected behavior?
Tibetan (and Dzongkha) should be in the supported locales, in order to be able to sort Tibetan and Dzongkha strings.

What went wrong?
Tibetan is not in the supported locales.

Did this work before? No 

Chrome version: 58.0.3029.110 (Build officiel) (64 bits)  Channel: dev
OS Version: Debian
Flash Version: 

The CLDR data for Dzongkha and Tibetan is large enough for inclusion, there is a Noto Font handling the script, there is even a ready spell checker on 

https://bugs.chromium.org/p/chromium/issues/detail?id=662850