We should apply the patch only when gerrit_repo and gerrit_ref are passed,
instead of using only the --apply-patch-on-gclient flag.

R=agable@chromium.org

Bug: 643346
Change-Id: I28547aed9daeefa2657a108e0bacbfd4fc9fa07e
Reviewed-on: https://chromium-review.googlesource.com/989667Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>