Change-Id: I2a4b279bd969483f4136d02b1e224ee342726b35
Cherry-Pick: github.com/golang/protobuf@75dceb112b174be156fa9952e66d3e99945572b4
Original-Author: Joe Tsai <joetsai@digital-static.net>
Reviewed-on: https://go-review.googlesource.com/c/151434


Reviewed-by: Damien Neil <dneil@google.com>