Passes toolstash -cmp.

Change-Id: I5b893b8b82b358534fd85542f05e3aa7e666bcd3
Reviewed-on: https://go-review.googlesource.com/26752
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>