Does 1.2 support p999 metrics?

[Tianying Chang]

Hi,

We want to expose p999 metrics for latency, e.g Get, Put, RPC latency. It
seems it only support up to p99. Is p999 only supported after 1.3?  If so,
any patch to port into 1.2 to enable this?

Thanks
Tian-Ying