Re-run tip gofmt to remove empty lines before the first comment in a
block (CL 71990).

Change-Id: I10bed93b88fd4fa4345f9f8f930c45db9f0d6e59
Reviewed-on: https://go-review.googlesource.com/76191
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>