presubmit: Make AUTHORS presubmit check use lower-cased email addresses.

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 87 matching lines @@
   """
   author = input_api.change.author_email
   if (author is None or author.endswith('@chromium.org') or
       author.endswith('@google.com')):
     return []
   authors_path = input_api.os_path.join(
       input_api.PresubmitLocalPath(), 'AUTHORS')
   valid_authors = (
       input_api.re.match(r'[^#]+\s+\<(.+?)\>\s*$', line)
       for line in open(authors_path))
-  valid_authors = [item.group(1) for item in valid_authors if item]
-  if not author in valid_authors:
+  valid_authors = [item.group(1).lower() for item in valid_authors if item]
+  if not author.lower() in valid_authors:
     return [output_api.PresubmitPromptWarning(
         ('%s is not in AUTHORS file. If you are a new contributor, please visit'
         '\n'
         'http://www.chromium.org/developers/contributing-code and read the '
         '"Legal" section\n'
         'If you are a chromite, verify the contributor signed the CLA.') %
         author)]
   return []
 
 
@@ skipping 21 matching lines @@
   results.extend(input_api.canned_checks.CheckChangeHasBugField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasTestField(
       input_api, output_api))
   results.extend(_CheckSubversionConfig(input_api, output_api))
   return results
 
 
 def GetPreferredTrySlaves():
   return ['win', 'linux', 'mac']