create activities from loggers themselves instead of passing the logger
as a constructor argument and allow direct construction of children, no
direct logger access needed. most call sites are not changed because we
still need to handle the "no parent" case, and the logger method can do
that more cleanly than a ternary at each site that creates an activity.
we may eventually want to create a root activity, which is cleaner too.
Change-Id: I295e056228dabb08a1316eba7973874784baa113
eldritch horrors
b73a7f1815