UserAgent: Mozilla/5.0 (X11; CrOS x86_64 11151.51.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.85 Safari/537.36
Platform: 11151.51.0 (Official Build) beta-channel celes

Steps to reproduce the problem:
1. As a Guest user in ChromeOS, go to chrome://settings/languages
2. Try to add a language
3. After confirmation, the list of languages remains unchanged

What is the expected behavior?
The language(s) selected should be added to the list of languages for the Guest user.

What went wrong?
Effectively, Guest users are unable to add any languages (or their related keyboard layouts), and are stuck on the default language.

Did this work before? N/A 

Chrome version: 71.0.3578.85  Channel: beta
OS Version: 11151.51.0
Flash Version: 32.0.0.101 

If the device owner were able to add additional languages for the Guest user (Bug 913193) this would not be as big an issue. As it stands, however, the Guest user is permanently stuck on the default language, and the device owner has no way (as far as I can tell) to help.