No functional changes here. Just makes next CL easier to read.

Change-Id: Icf7b2281b4da6cb59ff4edff05943b2ee288576a
Reviewed-on: https://go-review.googlesource.com/30945
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>