This is a follow-up to CL 38167.
Pure code movement.

Change-Id: I13e58f7eac6718c77076d89e13fc721a5205ec57
Reviewed-on: https://go-review.googlesource.com/38322
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>