Minor cleanup.

Change-Id: I7574f58a7e55c2bb798ebe9c7c98d36b8c258fb8
Reviewed-on: https://go-review.googlesource.com/21982
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>