Pass a list of strings rather than a string-as-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 gcl.
 """
 
@@ skipping 649 matching lines @@
 
 def _CheckHardcodedGoogleHostsInLowerLayers(input_api, output_api):
   def FilterFile(affected_file):
     """Filter function for use with input_api.AffectedSourceFiles,
     below.  This filters out everything except non-test files from
     top-level directories that generally speaking should not hard-code
     service URLs (e.g. src/android_webview/, src/content/ and others).
     """
     return input_api.FilterSourceFile(
       affected_file,
-      white_list=('^(android_webview|base|content|net)[\\\/].*'),
+      white_list=(r'^(android_webview|base|content|net)[\\\/].*', ),
       black_list=(_EXCLUDED_PATHS +
                   _TEST_CODE_EXCLUDED_PATHS +
                   input_api.DEFAULT_BLACK_LIST))
 
   pattern = input_api.re.compile('"[^"]*google\.com[^"]*"')
   problems = []  # items are (filename, line_number, line)
   for f in input_api.AffectedSourceFiles(FilterFile):
     for line_num, line in f.ChangedContents():
       if pattern.search(line):
         problems.append((f.LocalPath(), line_num, line))
@@ skipping 191 matching lines @@
       'win_aura',
       'win_rel',
   ]
 
   # Match things like path/aura/file.cc and path/file_aura.cc.
   # Same for chromeos.
   if any(re.search('[/_](aura|chromeos)', f) for f in files):
     trybots += ['linux_chromeos_clang:compile', 'linux_chromeos_asan']
 
   return trybots