Add a presubmit check that warns about declaring Singleton<T> in header files

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 glob
 import json
 import os
 import re
 import subprocess
@@ skipping 366 matching lines @@
 
   def testOnlyOwnersFiles(self):
     mock_change = MockChange([
       'some/path/OWNERS',
       'A\Windows\Path\OWNERS',
     ])
     results = PRESUBMIT.GetPreferredTryMasters(None, mock_change)
     self.assertEqual({}, results)
 
 
+class CheckSingletonInHeadersTest(unittest.TestCase):
+  def testSingletonInArbitraryHeader(self):
+    diff_singleton_h = ['base::subtle::AtomicWord '
+                        'Singleton<Type, Traits, DifferentiatingType>::']
+    diff_foo_h = ['// Singleton<Foo> in comment.',
+                  'friend class Singleton<Foo>']
+    diff_bad_h = ['Foo* foo = Singleton<Foo>::get();']
+    mock_input_api = MockInputApi()
+    mock_input_api.files = [MockFile('base/memory/singleton.h',
+                                     diff_singleton_h),
+                            MockFile('foo.h', diff_foo_h),
+                            MockFile('bad.h', diff_bad_h)]
+    warnings = PRESUBMIT._CheckSingletonInHeaders(mock_input_api,
+                                                  MockOutputApi())
+    self.assertEqual(1, len(warnings))
+    self.assertEqual('error', warnings[0].type)
+    self.assertTrue('Found Singleton<T>' in warnings[0].message)
+
+  def testSingletonInCC(self):
+    diff_cc = ['Foo* foo = Singleton<Foo>::get();']
+    mock_input_api = MockInputApi()
+    mock_input_api.files = [MockFile('some/path/foo.cc', diff_cc)]
+    warnings = PRESUBMIT._CheckSingletonInHeaders(mock_input_api,
+                                                  MockOutputApi())
+    self.assertEqual(0, len(warnings))
+
+
 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(
         MockInputApi(), MockFile('some/path/foo_platform.cc', lines))
     self.assertEqual(len(lines), len(errors))
@@ skipping 358 matching lines @@
     }
     for master, bots in bots.iteritems():
       for bot in bots:
         self.assertEqual(master, PRESUBMIT.GetTryServerMasterForBot(bot),
                          'bot=%s: expected %s, computed %s' % (
             bot, master, PRESUBMIT.GetTryServerMasterForBot(bot)))
 
 
 if __name__ == '__main__':
   unittest.main()