Use OldContents() for OWNERS files to do checks

BUG=141253
R=dpranke@chromium.org

Change-Id: Iacbc2f0571e725e4f2ccf5ea7878f101972289bb
Reviewed-on: https://chromium-review.googlesource.com/476610
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
diff --git a/git_cl.py b/git_cl.py
index ab98b45..426b752 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -5553,7 +5553,8 @@
           cl.GetChange(base_branch, None).AffectedFiles()],
       change.RepositoryRoot(),
       author, fopen=file, os_path=os.path,
-      disable_color=options.no_color).run()
+      disable_color=options.no_color,
+      override_files=change.OriginalOwnersFiles()).run()
 
 
 def BuildGitDiffCmd(diff_type, upstream_commit, args):