Passes toolstash -cmp.

Change-Id: Ie4675e6f713c3bbb90556f5347cbd7268a9c1a5d
Reviewed-on: https://go-review.googlesource.com/20357
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>