This is a "solution" to the "Chrome didn't shutdown correctly" after starting Chrome. It is a "solution" because it works but should be fixed somewhere else, preferably in systemd.

Certain processes termed as "applications" act more like services than applications. These applications include Chrome and Chromium: even when the application is closed it still leaves processes running in the background. Using the ps command reveals that these types of applications have a complex process tree and using killall ("killall google-chrome" or "killall chromium") doesn't properly kill these applications.

These types of applications should be stopped by "nicely" killing only the root process and after that wait for the root process to disappear from /proc. The script killgroup does just this: it tries to kill the oldest process with the TERM signal, wait for a predefined time (default max. 10 seconds) and only if that doesn't work kill with the KILL signal (forced kill).

There are three problems with systemd.

Problem 1:

I reported about the first original problem back in 2015. This problem was related to the mosh application. Then I used Ubuntu. Today I mostly use Arch Linux but these problems are probably still valid. The problem I reported back in 2015 was about systemd not sending KILL signal to "normal" processes. This can be proved with a simple tester script (here "tester") that writes (and flushes) to a file every time the KILL signal is received. This never happened at system shutdown/restart. I tried this again in 2018 and the same problem persists.

Problem 2:

The problem is caused by the fact that systemd doesn't wait for its own shutdown scripts to finish before tearing the processes down. Because of this the killgroup script must be run from Gnome shutdown script, from a bash alias ('alias myshutdown="killgroup chrome; sudo systemctl poweroff"') or from similar "middleware".

Problem 3:

This problem is the one "fixed" by the killgroup script. The killgroup script kills processes as trees and waits, unlike systemd. It is possible that systemd needs some added functionality to accomplish the same.

Copy the killgroup script to some accessible directory, i.e. /usr/local/bin or similar and make it executable ("cd /usr/local/bin", "sudo chown root:root killgroup", "sudo chmod 755 killgroup"). Then run this script as "killgroup google-chrome", "killgroup chromium" or similar: the name should match the name in the process tree (listed in ps a output).

The next step is to call the killgroup script from an alias, Gnome script or similar. An example of such a Gnome script is given here.