UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/68.0.3440.106 Chrome/68.0.3440.106 Safari/537.36

Steps to reproduce the problem:
Ubuntu Budgie 18.04, which only has Chromium browser installed by default and shows Chromium in Default Applications
1. Open Chromium

Could also reproduce on regular Ubuntu install after setting chromium-browser via update-alternatives

What is the expected behavior?
Chrome detects itself as default browser based on /etc/alternatives/x-www-browser -> /usr/bin/chromium-browser

~$ update-alternatives --display x-www-browser
x-www-browser - auto mode
  link best version is /usr/bin/chromium-browser
  link currently points to /usr/bin/chromium-browser
  link x-www-browser is /usr/bin/x-www-browser
/usr/bin/chromium-browser - priority 40

What went wrong?
Chrome does not detect that it is the default browser. Shows make default notification prompt.

Issue has been mentioned at https://unix.stackexchange.com/questions/110613/how-can-i-make-chrome-stop-asking-to-be-the-default-browser

Did this work before? N/A 

Chrome version: 68.0.3440.106  Channel: stable
OS Version: 
Flash Version: 

Also present with issue 812230, where Chromium was x-www-browser default in KDE