Debugged & wrote with Tom Bergan.

Updates golang/go#18083

Change-Id: I00a1cb748fe9c0f01c5bd4b8d1ac4438b56f1f8c
Reviewed-on: https://go-review.googlesource.com/33971
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tom Bergan <tombergan@google.com>