Hook up the presubmit check for empty descriptions.

PRESUBMIT.py

 # Copyright (c) 2011 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 Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 306 matching lines @@
       output_api,
       json_url='http://chromium-status.appspot.com/current?format=json'))
   results.extend(input_api.canned_checks.CheckRietveldTryJobExecution(input_api,
       output_api, 'http://codereview.chromium.org', ('win', 'linux', 'mac'),
       'tryserver@chromium.org'))
 
   results.extend(input_api.canned_checks.CheckChangeHasBugField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasTestField(
       input_api, output_api))
+  results.extend(input_api.canned_checks.CheckChangeHasDescription(

[M-A Ruel, 2011/12/06 01:56:12]

In fact, it's kind of pointless because the two checks above should fire anyway
on an empty description. So in any case, the dude bypassed presubmit checks.

[Lei Zhang, 2011/12/06 02:08:45]

The two tests above only results in a warning on commit. This one results in an
error.

+      input_api, output_api))
   results.extend(_CheckSubversionConfig(input_api, output_api))
   return results
 
 
 def GetPreferredTrySlaves(project, change):
   only_objc_files = all(
       f.LocalPath().endswith(('.mm', '.m')) for f in change.AffectedFiles())
   if only_objc_files:
     return ['mac']
   return ['win', 'linux', 'mac']