Make nt_registry Create/OpenRegKey return a scoped object

chrome_elf/chrome_elf_security.cc

 // Copyright 2013 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 "chrome_elf/chrome_elf_security.h"
 
 #include <assert.h>
 #include <windows.h>
 #include <versionhelpers.h>  // windows.h must be before
 
 #include "chrome_elf/chrome_elf_constants.h"
 #include "chrome_elf/nt_registry/nt_registry.h"
 
 namespace elf_security {
 
 void EarlyBrowserSecurity() {
   typedef decltype(SetProcessMitigationPolicy)* SetProcessMitigationPolicyFunc;
 
   // This function is called from within DllMain.
   // Don't do anything naughty while we have the loader lock.
   NTSTATUS ret_val = STATUS_SUCCESS;
-  HANDLE handle = INVALID_HANDLE_VALUE;
 
   // Check for kRegistrySecurityFinchPath.  If it exists,
   // we do NOT disable extension points.  (Emergency off flag.)
   if (nt::OpenRegKey(nt::HKCU, elf_sec::kRegSecurityFinchPath, KEY_QUERY_VALUE,
-                     &handle, &ret_val)) {
-    nt::CloseRegKey(handle);
+                     &ret_val)
+          .is_valid()) {
     return;
   }
 #ifdef _DEBUG
   // The only failure expected is for the path not existing.
   if (ret_val != STATUS_OBJECT_NAME_NOT_FOUND)
     assert(false);
 #endif
 
   if (::IsWindows8OrGreater()) {
     SetProcessMitigationPolicyFunc set_process_mitigation_policy =
         reinterpret_cast<SetProcessMitigationPolicyFunc>(::GetProcAddress(
             ::GetModuleHandleW(L"kernel32.dll"), "SetProcessMitigationPolicy"));
     if (set_process_mitigation_policy) {
       // Disable extension points in this process.
       // (Legacy hooking.)
       PROCESS_MITIGATION_EXTENSION_POINT_DISABLE_POLICY policy = {};
       policy.DisableExtensionPoints = true;
       set_process_mitigation_policy(ProcessExtensionPointDisablePolicy, &policy,
                                     sizeof(policy));
     }
   }
   return;
 }
 }  // namespace elf_security