Detecting Captive Portals

[Elroy Alva]

I'm actually building a custom AOSP Nougat build for the Nexus 6. This is for a small group of individuals and I want to save and automatically login to Captive Portals.  I've written most of the code to get and replay POST requests.
I however can't seem to figure out where the Sign-in notification is thrown or where the system checks for a captive portal.
It was pretty straightforward in ICS at http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.0.1_r1/android/net/wifi/WifiWatchdogStateMachine.java#WifiWatchdogStateMachine.isWalledGardenConnection%28%29
It seems more complex now. Any help here would be appreciated.

Thanks