Followon from CL 140306

Change-Id: Ic71033d2301105b15b60645d895a076107f44a2e
Reviewed-on: https://go-review.googlesource.com/c/142178
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>