How to distinguish the window "Registration on the network" android from the standard Browser?

Question

Android

I'm doing a hotspot. I do not want to lose the notification about the need to pass authorization. But at the same time, notify the user that it would be better to go through the Browser / Chrome / Opera in order to fill out the questionnaire and not get lost when reconnecting. In other words, you need cookies.
Android pulls http://host/generate_204 with an internal request (User-Agent: Dalvik), when a redirect is detected, it opens a window in which the User-Agent can no longer be distinguished from the built-in browser or chrome. What else can you get with javascript?
So far, there is only hope for this header:
X-Requested-With: com.android.captiveportallogin
True, you can’t work with it from javascript, and caching on the server is canceled altogether ..