ChromeOS system notifications (e.g. the one you see for downloads) can be right clicked on and disabled. This will dismiss the notification, but it doesn't actually disable said notification. Even if it did work, there would be no way to re-enable the notification because it doesn't show up in the settings panel (where, mysteriously, only screenshot shows up -- see bug 766846 ).
We should just disallow system notifications from being blocked.
Comment 1 by bugdroid1@chromium.org
, Oct 2 2017