Updates #5847.

Change-Id: Ic93f2e5f9a6aa3bd49cf75b16474ec5e897d17e1
Reviewed-on: https://go-review.googlesource.com/7940Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Rob Pike <r@golang.org>