Passes toolstash -cmp.

Update #14473.

Change-Id: I60ef7cac553b346ca6b8cc7152cd184e59994b66
Reviewed-on: https://go-review.googlesource.com/20216
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>