Change the "Missing OWNERS" presubmit check to only suggest owners for missing files.

tests/presubmit_unittest.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for presubmit_support.py and presubmit_canned_checks.py."""
 
 # pylint: disable=E1101,E1103
 
 import logging
@@ skipping 2476 matching lines @@
 
       if author_counts_as_owner:
         people.add(change.author_email)
         fake_db.files_not_covered_by(set(['foo/xyz.cc']),
             people).AndReturn(uncovered_files)
       else:
         people.discard(change.author_email)
         fake_db.files_not_covered_by(set(['foo/xyz.cc']),
             people).AndReturn(uncovered_files)
       if not is_committing and uncovered_files:
-        fake_db.reviewers_for(set(['foo/xyz.cc']),
+        fake_db.reviewers_for(set(['foo']),
             change.author_email).AndReturn(change.author_email)
 
     self.mox.ReplayAll()
     output = presubmit.PresubmitOutput()
     results = presubmit_canned_checks.CheckOwners(input_api,
         presubmit.OutputApi, author_counts_as_owner=author_counts_as_owner)
     if results:
       results[0].handle(output)
     self.assertEquals(output.getvalue(), expected_output)
 
@@ skipping 216 matching lines @@
         owners_check=False)
     self.assertEqual(1, len(results))
     self.assertEqual(
         'Found line ending with white spaces in:', results[0]._message)
     self.checkstdout('')
 
 
 if __name__ == '__main__':
   import unittest
   unittest.main()