No, but it would be "criminal conversion".
Is it? I see the little "personal size" bags of chips and cold, 20oz drinks, and I know the deli at our closest WM has little "carry cups" of popcorn chicken that are made for people to eat while in store.... That would almost constitute entrapment, wouldn't it? I think as long as you pay before exiting the store, you're OK. Probably a prosecutor decision, but I think the store would have a hard time making the case that you'd committed any crime by consuming any of those while you were still in the store. Not only that, I think they'd likely be opening themselves up to liability for wrongful prosecution.
Edit: On topic:
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