[Pkg-chromium-maint] Bug#669338: More info (conjecture?):

[David Baron]

It is not this service mode, per se, that is at fault (the "service" might 
have been installed as part of an effort to speed app startup, not by the 
maintainers). What eats 100% CPU is ONE object instance--the first one 
started?

Killall chromium did not kill the service and possible not this first instance 
(service previously killed explicitly), at least not in a short time. Had to 
be killed explicitly as well. This closed any remaining instances.