Added this locally but then broke the first rule of Gerrit
and clicked Submit instead of running "git submit".

Change-Id: I83c28d9151c566e9b2092e2613d67731a5d64beb
Reviewed-on: https://go-review.googlesource.com/129678
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>