Some minor scoping cleanups found by a very old version of grind.

Change-Id: I1d373817586445fc87e38305929097b652696fdd
Reviewed-on: https://go-review.googlesource.com/21064
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>