It really depends on the cat.
My cat is free-fed, meaning there is a full food bowl available at all times. He is overweight. I bought him a special interactive feeder bowl, which forces him to work for every paw-ful of food he eats... and he is still overweight, though he did lose a little.
Here are some things to consider when trying to figure out if your cat has self control.
First, this is a weakness that many humans have - we eat when we're bored, when we're stressed, when we want to celebrate, etc. Cats absolutely do that, too. Dogs, too. In fact, there are some dog breeds (entire breeds!) that are simply known for being food-obsessed, like beagles and labs. My brother has a dog that will literally eat until it throws up, and then will eat some more. It just depends on how food-oriented or food-obsessed the individual is.
Second, if this is a high-value, unusual treat, then all bets are off. There are some people that, if you put a cake in front of them, they will eat until the cake is gone - a slice here, a nibble there and a few hours later, no more cake.
Third, it is important to remember that before the comforts and conveniences of our modern world developed, we humans and our pets had to work for hours to get a meal. It is actually unnatural to simply walk up to a bowl of food and eat until you are full and then have to find a way to occupy yourself for the rest of the day.
On a separate but related note, be careful that the food you are giving your cat is safe and non-toxic. (not spoiled, bone-free) You can find a list of cat-safe foods on google easily. Also, remember that if this is an unusual or special treat, that too much of it could make your kitty sick enough to make messes all over your house, so moderation is best.