Add UTF8String to the banned method list.

PRESUBMIT.py

 # 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.
 
 """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 depot_tools.
 """
 
@@ skipping 129 matching lines @@
     ),
     (
       'convertSizeToBase:',
       (
        'The use of -[NSView convertSizeToBase:] is almost certainly wrong.',
        'Please use |convertSize:(point) toView:nil| instead.',
        'http://dev.chromium.org/developers/coding-style/cocoa-dos-and-donts',
       ),
       True,
     ),
+    (
+      r"/\s+UTF8String\s*]",
+      (
+       'The use of -[NSString UTF8String] is dangerous as it can return null',
+       'even if |canBeConvertedToEncoding:NSUTF8StringEncoding| returns YES.',
+       'Please use |SysNSStringToUTF8| instead.',
+      ),
+      True,
+    ),
 )
 
 
 _BANNED_CPP_FUNCTIONS = (
     # Make sure that gtest's FRIEND_TEST() macro is not used; the
     # FRIEND_TEST_ALL_PREFIXES() macro from base/gtest_prod_util.h should be
     # used instead since that allows for FLAKY_ and DISABLED_ prefixes.
     (
       'FRIEND_TEST(',
       (
@@ skipping 2140 matching lines @@
   results.extend(input_api.canned_checks.CheckTreeIsOpen(
       input_api,
       output_api,
       json_url='http://chromium-status.appspot.com/current?format=json'))
 
   results.extend(input_api.canned_checks.CheckChangeHasBugField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasDescription(
       input_api, output_api))
   return results