Also removes unnecessary allocation.

Change-Id: I3406cf75a7b64d93b2b99c7f1f5c78f580452b60
Reviewed-on: https://go-review.googlesource.com/30891
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>