partially addresses #16360

Change-Id: I8274825b9ca6aec46294c8513b4795b0eb3062a2
Reviewed-on: https://go-review.googlesource.com/28992Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>