How can I disable the "Chromium didn’t shut down correctly" message when my browser opens?

Much easier solution, start Chromium with the --disable-infobars flag. I tried all of the above before finding it, and it does exactly what I wanted. You can leave all of the other stuff alone.

My specific command line is:

/usr/bin/chromium-browser --start-fullscreen --disable-session-crashed-bubble --disable-infobars http://www.example.com

Also, apparently running in incognito mode by default will also prevent the error because nothing is saved from the session against which to check for a crash.

example: chromium-browser --kiosk --start-maximized --incognito kiosk.html

This finally worked for me, and it's pretty simple:

1. Shut down Chromium gracefully
2. Change the "Change content" permissions of ~/.config/chromium/Default/Preferences to "Nobody"

That will lock the state of two variables, regardless of how Chromium was shut down:

• "exit_type": "Normal"
• "exited_cleanly": true

Of course, only do that after you're done setting preferences

Solution/Hack in 5 seconds (https://askubuntu.com/a/720855) Settings->Advanced Settings->System-> uncheck Continue running background apps when Chrome is closed

(read the whole thread for hints on why the issue happens. Makes a lot of sense)