Make CloudPolicyValidator memory management clearer

chrome/browser/chromeos/policy/device_local_account_policy_store.cc

 // 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.
 
 #include "chrome/browser/chromeos/policy/device_local_account_policy_store.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 194 matching lines @@
                              CloudPolicyValidatorBase::DM_TOKEN_REQUIRED);
 
   // Validate the device id to match what device policy has.
   validator->ValidateDeviceId(device_policy_data->device_id(),
                               CloudPolicyValidatorBase::DEVICE_ID_REQUIRED);
 
   validator->ValidatePayload();
   validator->ValidateSignature(key->as_string());
 
   if (validate_in_background) {
-    // The Validator will delete itself once validation is
-    // complete.
-    validator.release()->StartValidation(
-        base::Bind(callback, key->as_string()));
+    UserCloudPolicyValidator::StartValidation(
+        std::move(validator), base::Bind(callback, key->as_string()));
   } else {
     validator->RunValidation();
 
     UpdatePolicy(key->as_string(), validator.get());
   }
 }
 
 }  // namespace policy