UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36
Platform: 7834.70.0 (official build)

Steps to reproduce the problem:
1. Because the default keyboard is English, could we change the default?
2. We use chrome license for public session. It ask us to choose "Phonetic" or "Cangjie", because the default is American Keyboard.
3. The question is that, after we choose default = Traditional Chinese, we need to choose "Phonetic" or "Cangjie", because the default value is American Keyboard.

What is the expected behavior?
Users don't want to be  prompted to choose keyboard when every time login.

What went wrong?
User always are prompted to choose keyboard when every time login.

Did this work before? No 

Chrome version: 49.0.2623.112  Channel: stable
OS Version: 49.0.2623.112
Flash Version: Flash 21.0.0.216-r1

Ricardo ever suggest me to do this:
After reviewing the details provided about your case, the process required is able to be performed, and you can use the following steps to setup this feature:

1. Within the Google Apps Admin Console, go to the "Device Management" section.
2. Within the Device Management, select the "Chrome Management" option on the left end side of the page.
3. Once you are within the Chrome Management, select the option "Public Session Settings".
4. Scroll down or search for the option "Session Locale". Within this section you will have the Language and Keyboard settings required.
5. Once the settings are changed, go to one of the affected devices and go to the page Chrome://policy.
6. Select the option "Reload Policies" and restart the device.
7. Reproduce your issue again.

If after performing the above steps you are still facing issues, or if you have any other questions, please reply to this message and I will gladly attempt to reach you over the phone in order to discuss this case.

I hope that this information is useful, but if you have further questions about your case, please reply to this message and I will gladly assist you further.

But he also told that:
In addition to the steps sent on my last message and after testing your issue further on our end, unfortunately the additional changes that you need to perform with the Keyboard settings cannot be done.

With this in mind, I suggest accessing the page http://crbug.com and submit a feature request with our development team directly. Once this task is complete a member of the team will verify if this option can be performed for the devices, as well as to be applied as a Chrome related policy.

I hope that this information is useful, but if you have further questions about your case, please reply to this message and I will gladly assist you further.