What was Mr. Gilmer's closing argument in To Kill a Mockingbird (because it was never in the book)?

When Scout asks about Mr. Gilmer's cross examination and/or closing argument, Jem says "Sh-h. Nothing new, just the usual. Hush now." We can expect that Mr. Gilmer's closing argument would reiterate some of the points he tried to make during his sessions with Mayella, Bob, and Tom Robinson. Gilmer would probably bring up that Tom had once served thirty days for disorderly conduct. He might try to suggest that this shows Tom's tendency to be violent. Gilmer calls Tom "boy" when he questions him. This either shows Gilmer's inherent racist attitude or his attempts to put Tom in an inferior position. 

In his summation, Gilmer would probably make Mayella as sympathetic as he can, making her look like a helpless victim. He might also appeal to the jury's own biases and suggest that Tom was acting on his own simplistic instincts and urges. In other words, Gilmer might use loaded language in order to suggest that Tom, a black man, was doing what black men are predisposed to do. This is a racist tactic but it is something Gilmer might employ to appeal to the racist attitudes of the jurists.