Per Jeremy's comment in CL 199643. This makes the code read
better.

Change-Id: If270aecd712a27fb52e3faf5a4339200327d9ffe
Reviewed-on: https://go-review.googlesource.com/c/go/+/201023
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>