Enable OWNERS file enforcement in depot_tools

PRESUBMIT.py

 # Copyright (c) 2010 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.
 
 """Top-level presubmit script for depot tools.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into gcl.
 """
 
@@ skipping 14 matching lines @@
   output = []
   # Verify that LocalPath() is local, e.g.:
   #   os.path.join(PresubmitLocalPath(), LocalPath()) == AbsoluteLocalPath()
   for i in input_api.AffectedFiles():
     if (input_api.os_path.join(input_api.PresubmitLocalPath(), i.LocalPath()) !=
         i.AbsoluteLocalPath()):
       output.append(output_api.PresubmitError('Path inconsistency'))
       # Return right away because it needs to be fixed first.
       return output
 
-  # TODO(dpranke): uncomment and enable :).
-  #
-  # output.extend(input_api.canned_checks.CheckOwners(
-  #     input_api,
-  #     output_api))
+  output.extend(input_api.canned_checks.CheckOwners(input_api, output_api))
 
   output.extend(input_api.canned_checks.RunPythonUnitTests(
       input_api,
       output_api,
       UNIT_TESTS))
   output.extend(WasGitClUploadHookModified(input_api, output_api))
 
   white_list = [r'.*\.py$', r'^git-try$']
   black_list = list(input_api.DEFAULT_BLACK_LIST) + [
       r'^cpplint\.py$',
@@ skipping 22 matching lines @@
 
 
 def WasGitClUploadHookModified(input_api, output_api):
   for affected_file in input_api.AffectedSourceFiles(None):
     if (input_api.os_path.basename(affected_file.LocalPath()) ==
         'git-cl-upload-hook'):
       return [output_api.PresubmitPromptWarning(
           'Don\'t forget to fix git-cl to download the newest version of '
           'git-cl-upload-hook')]
   return []