Suggestions:
If you have RCC access, check out the United RCC at the hub in T3. Do not go out of security after your arriving flight, once you do your AC ticket may not get you back in. They should be able to check if your outgoing YYZ flight is on time there.
If you don't, one of the food courts in the new International terminal may be your best bet. Follow the signs to the IT, when it's time for your AC flight go to Terminal 1.