Remove the "not_after" validation of policy timestamps

chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.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_cloud_policy_store_chromeos.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 50 matching lines @@
     NotifyStoreError();
     return;
   }
 
   std::unique_ptr<DeviceCloudPolicyValidator> validator(
       CreateValidator(policy));
   validator->ValidateSignatureAllowingRotation(
       public_key->as_string(), install_attributes_->GetDomain());
   validator->ValidateAgainstCurrentPolicy(
       device_settings_service_->policy_data(),
-      CloudPolicyValidatorBase::TIMESTAMP_FULLY_VALIDATED,
+      CloudPolicyValidatorBase::TIMESTAMP_VALIDATED,
       CloudPolicyValidatorBase::DM_TOKEN_REQUIRED,
       CloudPolicyValidatorBase::DEVICE_ID_REQUIRED);
   DeviceCloudPolicyValidator::StartValidation(
       std::move(validator),
       base::Bind(&DeviceCloudPolicyStoreChromeOS::OnPolicyToStoreValidated,
                  weak_factory_.GetWeakPtr()));
 }
 
 void DeviceCloudPolicyStoreChromeOS::Load() {
   device_settings_service_->Load();
@@ skipping 155 matching lines @@
     UMA_HISTOGRAM_BOOLEAN(kDMTokenCheckHistogram, true);
   } else {
     LOG(ERROR) << "Device policy read on enrolled device yields "
                << "no DM token! Status: " << service_status << ".";
     chromeos::StartupUtils::MarkEnrollmentRecoveryRequired();
     UMA_HISTOGRAM_BOOLEAN(kDMTokenCheckHistogram, false);
   }
 }
 
 }  // namespace policy