They should be fine. If any of my birds venture close enough to the road, they will eat up the cherries that taste like gasoline... and to no ill effect.
I am glad to hear it. Usually the OEGB only goes for the bugs! LOL! Don't know why it ate the pits, except that the kids were spitting them (gross!) so she was jumping on them and they thought it was hilarious. "Oooh! Look the chicken ate my spit!"
I give my chickens the cherries that fall from my cherry tree. They just love them. They can't eat them fast enough. I don't worry at all about the "pits". Don't worry your chicken will be just fine. I am sure they were happy about their "yummy" treat!