This of course is a complete mismatch. The question was how long would the ref let the beating go. Cobb would take a serious beating. My guess is the ref stops this somewhere by the third round. Cobb might even hit the canvas.
Just because you have a solid jaw doesnt mean you cant be stopped. It happens all the time and as others pointed out Foreman stopped Chuvalo who had probably the best chin ever. Look at say Vitali vs Sanders for someone getting there ass whipped and just takes too much punishment until the ref stops it. Cobb would get his ass beat and stopped one way or another. Maybe he never gets knocked down but that doesnt mean the ref or his corner doesnt stop it eventually