upstream git hash: 1775db3f06b568179d273425900dd09125831dd5

Update #17490

Change-Id: I95e3c57137756c5c7a9b7334075caef66f205231
Reviewed-on: https://go-review.googlesource.com/c/156365
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>