The existing nested loops are too tricky for me to grok and don't seem
necessary.

Change-Id: I75c65c8470b799d6f4cfb05bb1b4796c5d7d32e7
Reviewed-on: https://go-review.googlesource.com/19927
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>