UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36

Steps to reproduce the problem:
Devtool cannot customize device/browser locale.

What is the expected behavior?
As well as UserAgent, locale can be customized.

What went wrong?
I want to reproduce a problem at end-users in a foreign country.

Did this work before? N/A 

Chrome version: 66.0.3359.139  Channel: stable
OS Version: OS X 10.12.6
Flash Version: