The previous code did not distinguish between None and [] value for orig_deps.

This could be triggered by not having any deps, but some entries in deps_os,
in which case these deps_os entries would get added by mistake to deps.

Bug: 570091
Change-Id: Id5b41e37ea717d5d00404694ad5bfce8df9da934
Reviewed-on: https://chromium-review.googlesource.com/558349Reviewed-by: Michael Moss <mmoss@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Paweł Hajdan Jr. <phajdan.jr@chromium.org>