Add first changes needed for OWNERS file support.

presubmit_canned_checks.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.
 
 """Generic presubmit checks that can be reused by other presubmit checks."""
 
 ### Description checks
 
 def CheckChangeHasTestField(input_api, output_api):
   """Requires that the changelist have a TEST= field."""
@@ skipping 606 matching lines @@
     pending_builds_len = len(builder.get('pending_builds', []))
     if pending_builds_len > max_pendings:
       out.append('%s has %d build(s) pending' %
                   (builder_name, pending_builds_len))
   if out:
     return [output_api.PresubmitPromptWarning(
         'Build(s) pending. It is suggested to wait that no more than %d '
             'builds are pending.' % max_pendings,
         long_text='\n'.join(out))]
   return []
+
+
+def CheckOwners(input_api, output_api):
+  affected_files = set(input_api.change.AffectedFiles())
+  owners_db = input_api.owners_db
+
+  if input_api.is_commiting:
+    missing_files = owners_db.FilesNotCoveredBy(affected_files,
+                                                input_api.change.approvers)
+    if missing_files:
+      return [output_api.PresubmitPromptWarning('Missing approvals for: %s' %
+              ','.join(missing_files))]
+    return []
+  else:
+    if not input_api.change.get('R', None):
+      suggested_reviewers = owners_db.OwnersFor(affected_files)
+
+      # TODO(dpranke): consider getting multiple covering sets of reviewers
+      # and displaying them somehow?
+      input_api.change['R'] = ','.join(suggested_reviewers)