Add Windows 10 build number to user-agent

base/sys_info_win.cc

 // Copyright 2015 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 "base/sys_info.h"
 
 #include <windows.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 135 matching lines @@
   return win::OSInfo::GetInstance()->allocation_granularity();
 }
 
 // static
 void SysInfo::OperatingSystemVersionNumbers(int32_t* major_version,
                                             int32_t* minor_version,
                                             int32_t* bugfix_version) {
   win::OSInfo* os_info = win::OSInfo::GetInstance();
   *major_version = os_info->version_number().major;
   *minor_version = os_info->version_number().minor;
-  *bugfix_version = 0;
+  *bugfix_version = os_info->version_number().build;
 }
 
 }  // namespace base