The autocomplete module listens to keypress events for both printable keys
and non-printable keys a lot. However, we're stopping dispatching keypress
events for non-printable keys in the default event group of web content.
This means that autocomplete should listen to keypress events in the
system event group.
Note that it's difficult to globally change keypress event listeners to
keydown event listeners because if we stop keypress events at preceding
keydown event in autocomplete or satchel modules, some other modules
fail to handle keydown or keypress events before autocomplete, and it's
not easy to investigate which keypress event listener in which modules
should be changed to a keydown event listener.
Therefore, this patch doesn't do that, and uses the event group approach.
Moonchild
roytam1