ui: Fix missing import of 're' module.

ui/PRESUBMIT.py

 # Copyright 2015 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.
 
 """Presubmit script for ui.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
 INCLUDE_CPP_FILES_ONLY = (
   r'.*\.(cc|h|mm)$',
 )
 
 def CheckScopedPtr(input_api, output_api,
                    white_list=INCLUDE_CPP_FILES_ONLY, black_list=None):
   black_list = tuple(black_list or input_api.DEFAULT_BLACK_LIST)
   source_file_filter = lambda x: input_api.FilterSourceFile(x,
                                                             white_list,
                                                             black_list)
   errors = []
   for f in input_api.AffectedSourceFiles(source_file_filter):
     for line_number, line in f.ChangedContents():
       # Disallow:
       # scoped_ptr<T>()
-      if re.search(r'\bscoped_ptr<.*?>\(\)', line):
+      if input_api.re.search(r'\bscoped_ptr<.*?>\(\)', line):
         errors.append(output_api.PresubmitError(
           '%s:%d uses scoped_ptr<T>(). Use nullptr instead.' %
           (f.LocalPath(), line_number)))
   return errors
 
 
 def CheckChange(input_api, output_api):
   results = []
   results += CheckScopedPtr(input_api, output_api)
   return results
 
 
 def CheckChangeOnUpload(input_api, output_api):
   return CheckChange(input_api, output_api)
 
 
 def CheckChangeOnCommit(input_api, output_api):
   return CheckChange(input_api, output_api)