Dynamic TLS record size tuning

From igrigorik in TS-2365:

FWIW, I think you may be interested in this discussion:

• http://mailman.nginx.org/pipermail/nginx-devel/2013-December/004703.html
• http://mailman.nginx.org/pipermail/nginx-devel/2014-January/004748.html

In a nutshell, static record size introduces an inherent tradeoff between latency and throughput – smaller records are good for latency, but hurt server throughput by adding bytes and CPU overhead. It would be great if we could implement a smarter strategy in ATS. The extra benefit is that it's one less knob to tune: the out-of-the-box experience would be better optimized for all ATS users, regardless of mix/type of traffic being proxies.