Remove remnants of dead downstream_cache_lifetime_ms. (It's not registered or used anywhere)
Remove remnants of dead downstream_cache_lifetime_ms.
(It's not registered or used anywhere)

crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp,crowell/modpagespeed_tmp