The EPA drinking water limit is 4 ppm FC assuming one drinks 2 liters (or quarts) per day every day for a lifetime. That's set so that the lifetime cancer risk doesn't increase by more than around 1 in a million. So while not something to do regularly, if the dog drinks pool water with the elevated chlorine level it probably won't have a negative effect unless the chlorine amount was enough to make it to the intestines where it would kill bacteria. That would be like taking antibiotics where you'd want to replenish by eating yoghurt or taking probiotics.

As shown in this PDF file, drinking bleach is in the top 10 toxicoses in dogs, but bleach is at around 86,000 ppm FC so clearly much higher than the shock level in a pool.