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

chrome/installer/util/install_util.cc

 // 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.
 //
 // See the corresponding header file for description of the functions in this
 // file.
 
 #include "chrome/installer/util/install_util.h"
 
 #include <shellapi.h>
@@ skipping 118 matching lines @@
   } else {
     DCHECK_EQ(ERROR_FILE_NOT_FOUND, result);
     VLOG(1) << "No existing " << dist->GetApplicationName()
             << " install found.";
   }
 
   return ret;
 }
 
 bool InstallUtil::IsOSSupported() {
-  int major, minor;
   base::win::Version version = base::win::GetVersion();
-  base::win::GetServicePackLevel(&major, &minor);
+  const int* service_pack = base::win::OSInfo::GetInstance()->service_pack();
 
   // We do not support Win2K or older, or XP without service pack 2.
   VLOG(1) << "Windows Version: " << version
-          << ", Service Pack: " << major << "." << minor;
+          << ", Service Pack: " << service_pack[0] << "." << service_pack[1];
   return (version > base::win::VERSION_XP) ||
-      (version == base::win::VERSION_XP && major >= 2);
+      (version == base::win::VERSION_XP && service_pack[0] >= 2);
 }
 
 void InstallUtil::WriteInstallerResult(bool system_install,
                                        const std::wstring& state_key,
                                        installer::InstallStatus status,
                                        int string_resource_id,
                                        const std::wstring* const launch_cmd) {
   const HKEY root = system_install ? HKEY_LOCAL_MACHINE : HKEY_CURRENT_USER;
   DWORD installer_result = (GetInstallReturnCode(status) == 0) ? 0 : 1;
   scoped_ptr<WorkItemList> install_list(WorkItem::CreateWorkItemList());
@@ skipping 226 matching lines @@
   int len = GetDateFormatW(LOCALE_INVARIANT, 0, NULL, kDateFormat,
                            date_str, arraysize(date_str));
   if (len) {
     --len;  // Subtract terminating \0.
   } else {
     PLOG(DFATAL) << "GetDateFormat";
   }
 
   return std::wstring(date_str, len);
 }