This is a followup to https://go-review.googlesource.com/37038.

Updates #19435.

Change-Id: If3d56bca0e8816d1a169f5cf97f27b20695a9955
Reviewed-on: https://go-review.googlesource.com/43692Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>