I'd trash it. I like to bomb descents, and I don't want to have to be wondering if / when my tire will blow out next.

If it's any consolation, earlier this year I threw away a tire with only 250 miles due to a sidewall cut that let the tube protrude through. I could have booted it and ridden it for some more miles, but I felt the structural integrity of the casing was compromised. That's not something a 200 pound rider wants to be thinking about while leaning in to a corner at 35 - 40 mph or so.