I recommend mentioning it to the recruiter or phone screen person who you make initial contact with. Often times, this person is from HR and is well-versed in the legal obligations of he company surrounding equal opportunity employment. And, they can make sure the onsite interviews can accommodate any special needs you might have.
If you don't need to disclose for special accommodations during the interview, then there is typically a form that's filled out either with the application or upon accepting a position to ensure the company is follow equal ppportunity practices. So, it usually asks about race, gender, military involvement, disability, etc. You can choose not to bring it up if it isn't relevant and answer it then.
However, you can always wait until you are asked the typical strengths and weaknesses question...or name a time when you had to overcome a challenge. It would be very good to say that despite the limitation, you are still able to finish work ahead of deadlines. Emphasizing that despite having to take a few breaks during the day, you can still meet deadlines and exceed expectations...it works strongly in your favor.
Hope that helps.