Make the windows_version.h functions threadsafe by using a singleton.

sandbox/src/integrity_level_test.cc

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
 #include <windows.h>
 #include <atlsecurity.h>
 
 #include "base/win/windows_version.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "sandbox/src/sandbox.h"
 #include "sandbox/src/sandbox_policy.h"
@@ skipping 26 matching lines @@
 
   ::LocalFree(sid_low);
 
   if (is_low_sid)
     return SBOX_TEST_SUCCEEDED;
 
   return SBOX_TEST_DENIED;
 }
 
 TEST(IntegrityLevelTest, TestLowILReal) {
-  if (base::win::VERSION_VISTA != base::win::GetVersion())
+  if (base::win::GetVersion() != base::win::VERSION_VISTA)
     return;
 
   TestRunner runner(JOB_LOCKDOWN, USER_INTERACTIVE, USER_INTERACTIVE);
 
   runner.SetTimeout(INFINITE);
 
   runner.GetPolicy()->SetIntegrityLevel(INTEGRITY_LEVEL_LOW);
 
   EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"CheckIntegrityLevel"));
 
   runner.SetTestState(BEFORE_REVERT);
   EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"CheckIntegrityLevel"));
 }
 
 TEST(DelayedIntegrityLevelTest, TestLowILDelayed) {
-  if (base::win::VERSION_VISTA != base::win::GetVersion())
+  if (base::win::GetVersion() != base::win::VERSION_VISTA)
     return;
 
   TestRunner runner(JOB_LOCKDOWN, USER_INTERACTIVE, USER_INTERACTIVE);
 
   runner.SetTimeout(INFINITE);
 
   runner.GetPolicy()->SetDelayedIntegrityLevel(INTEGRITY_LEVEL_LOW);
 
   EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"CheckIntegrityLevel"));
 
   runner.SetTestState(BEFORE_REVERT);
   EXPECT_EQ(SBOX_TEST_DENIED, runner.RunTest(L"CheckIntegrityLevel"));
 }
 
 TEST(IntegrityLevelTest, TestNoILChange) {
-  if (base::win::VERSION_VISTA != base::win::GetVersion())
+  if (base::win::GetVersion() != base::win::VERSION_VISTA)
     return;
 
   TestRunner runner(JOB_LOCKDOWN, USER_INTERACTIVE, USER_INTERACTIVE);
 
   runner.SetTimeout(INFINITE);
 
   EXPECT_EQ(SBOX_TEST_DENIED, runner.RunTest(L"CheckIntegrityLevel"));
 }
 
 }  // namespace sandbox