Updates #20821

Change-Id: I77a5b9a3bbb931845ef52a479549d71069af9540
Reviewed-on: https://go-review.googlesource.com/46913
Run-TryBot: Shawn Walker-Salas <shawn.walker@oracle.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>