Add PRESUBMIT.py warning for contradictory NOTREACHED() use.

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 375 matching lines @@
     self.assertTrue(':1 OS_WINDOWS' in errors[0])
     self.assertTrue('(did you mean OS_WIN?)' in errors[0])
 
   def testValidOSMacroNames(self):
     lines = ['#if defined(%s)' % m for m in PRESUBMIT._VALID_OS_MACROS]
     errors = PRESUBMIT._CheckForInvalidOSMacrosInFile(
         MockInputApi(), MockFile('some/path/foo_platform.cc', lines))
     self.assertEqual(0, len(errors))
 
 
+class CheckContradictoryNotreachedUseTest(unittest.TestCase):
+  def testValid(self):
+    lines = [r'{',
+             r"  char a = '\\', b = '\0', c = '\'';",
+             r'  char d[] = "NOTREACHED();";',
+             r'  NOTREACHED(); // NOTREACHED();',
+             r'  /* NOTREACHED(); */',
+             r'  // line continuation \\',
+             r'  still inside comment',
+             r'  // comment followed by empty line',
+             r'',
+             r'}',
+             r'switch (i) {',
+             r'  case 7: NOTREACHED(); break;',
+             r'}']
+    output = PRESUBMIT._CheckContradictoryNotreachedUseInFile(
+        MockInputApi(), MockFile('some/path/foo_platform.cc', lines))
+    self.assertEqual(0, len(output))
+
+  def testInvalid(self):
+    lines = ['{',
+             '  NOTREACHED();',
+             '  return;',
+             '}',
+             '{',
+             '  NOTREACHED();',
+             '  /* */',
+             '  return;',
+             '  /* */',
+             '}',
+             'switch (i) {',
+             '  case 7: NOTREACHED(); some_thing(); break;',
+             '}']
+    output = PRESUBMIT._CheckContradictoryNotreachedUseInFile(
+        MockInputApi(), MockFile('some/path/foo_platform.cc', lines))
+    self.assertEqual(3, len(output))
+
+
 class CheckAddedDepsHaveTetsApprovalsTest(unittest.TestCase):
   def testFilesToCheckForIncomingDeps(self):
     changed_lines = [
       '"+breakpad",',
       '"+chrome/installer",',
       '"+chrome/plugin/chrome_content_plugin_client.h",',
       '"+chrome/utility/chrome_content_utility_client.h",',
       '"+chromeos/chromeos_paths.h",',
       '"+components/breakpad",',
       '"+components/nacl/common",',
@@ skipping 20 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()