Change top-level PRESUBMIT to support split tryserver

PRESUBMIT_test.py

 #!/usr/bin/env python
 # 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.
 
 import os
 import re
 import unittest
 
 import PRESUBMIT
@@ skipping 351 matching lines @@
       MockFile('other/path/qux.cc', ''),
     ]
     results = PRESUBMIT._CheckPatchFiles(mock_input_api, MockOutputApi())
     self.assertEqual(0, len(results))
 
   def testOnlyOwnersFiles(self):
     mock_change = MockChange([
       'some/path/OWNERS',
       'A\Windows\Path\OWNERS',
     ])
-    results = PRESUBMIT.GetPreferredTrySlaves(None, mock_change)
-    self.assertEqual(0, len(results))
+    results = PRESUBMIT.GetPreferredTryMasters(None, mock_change)
+    self.assertEqual({}, results)
 
 
 class InvalidOSMacroNamesTest(unittest.TestCase):
   def testInvalidOSMacroNames(self):
     lines = ['#if defined(OS_WINDOWS)',
              ' #elif defined(OS_WINDOW)',
              ' # if defined(OS_MACOSX) || defined(OS_CHROME)',
              '# else  // defined(OS_MAC)',
              '#endif  // defined(OS_MACOS)']
     errors = PRESUBMIT._CheckForInvalidOSMacrosInFile(
@@ skipping 42 matching lines @@
       'policy/DEPS',
       'sandbox/DEPS',
       'tools/memory_watcher/DEPS',
       'third_party/lss/linux_syscall_support.h',
     ])
     self.assertEqual(expected, files_to_check);
 
 
 if __name__ == '__main__':
   unittest.main()