Example URL:

Steps to reproduce the problem:
1. Enable data save function (if not already).
2. Connect to free wifi hotspot network.
3. Try to visit login page (via system popup).
4. Error message / blank page

What is the expected behavior?
In an wifi hotspot (captive portal) network, the browser must not use the data save server/proxy to access the login page.

What went wrong?
Android device connects to wifi network, tries to find out if there is a captive portal (GET /generate_204 from Google Server). The captive portal redirects the request to the login page (e.g. http://login.wifi) --> Android Popup "Login to network" appears. By trying to login, the browser (chrome) is launched and tries to load the login page (e.g. http://login.wifi) by using the data save server as proxy. This (of course) cannot work, because till now there war no login.

If data save option is diabled, everthing works fine.

So in my opionen the browser (chrome) must (of course) not use the data save server as proxy if the device OS (android)  "knows" it has to login before getting access to the internet.

Did this work before? N/A 

Chrome version: 61.0.3163.98  Channel: n/a
OS Version: 7.0.0
Flash Version: