I want to be able to set proxy.config.http.keep_alive_no_activity_timeout_out per-transaction

I want to be able to set this the same as you can set proxy.config.http.keep_alive_no_activity_timeout_in.
I have a patch, but it just turns off a couple of calls, which seems wrong because I suspect that those calls are supposed to re-set the 'active'-ness of the connections, but it works reasonably for me even so. (The calls are disabled because they are being made after the code doesn't have a transaction to check the config in.)