Derived	from Naoki's reproducer.

Update #29362

Change-Id: I1cbd33b38a2f74905dbc22c5ecbad4a87a24bdd1
Reviewed-on: https://go-review.googlesource.com/c/156122
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>