Check license header for .go files.

TEST=unittest
TEST=manually checked repo upload fails if license header is missing in
a go file, and success otherwise.
BUG=chromium:979452

Change-Id: Ic1f81fce7bbba88f799677d72e2ce2f241134f1d
Reviewed-on: https://chromium-review.googlesource.com/1679931
Tested-by: Keigo Oka <oka@chromium.org>
Commit-Ready: Keigo Oka <oka@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed