Updates golang/go#16218

Change-Id: I613cf0a65d40a9823c83e0a547fbd48b2236d16e
Reviewed-on: https://go-review.googlesource.com/49630Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>