Added a regression test. Simplified some logic - if we don't add os-specific
deps and hooks to |dependencies|, we don't need to keep separate original values.

Bug: 570091
Change-Id: I5bdd0b6a66df6b3a2b99d0ad9c6e54ee7114f09b
Reviewed-on: https://chromium-review.googlesource.com/581687
Commit-Queue: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Michael Moss <mmoss@chromium.org>