This is preliminary cleanup for another change.

No functional changes. Passes toolstash -cmp.

Change-Id: I11d562fbd6cba5c48d9636f3149e210e5f5308ad
Reviewed-on: https://go-review.googlesource.com/7696Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>