Use {To/From}JavaTime for policy timestamps

chrome/browser/chromeos/policy/device_cloud_policy_manager_chromeos_unittest.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_manager_chromeos.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 412 matching lines @@
         store_result_(true),
         status_(EnrollmentStatus::ForStatus(EnrollmentStatus::SUCCESS)),
         done_(false) {}
 
   void SetUp() override {
     DeviceCloudPolicyManagerChromeOSTest::SetUp();
 
     // Set up test data.
     device_policy_.SetDefaultNewSigningKey();
     device_policy_.policy_data().set_timestamp(
-        (base::Time::NowFromSystemTime() -
-         base::Time::UnixEpoch()).InMilliseconds());
+        base::Time::NowFromSystemTime().ToJavaTime());
     device_policy_.Build();
 
     register_response_.mutable_register_response()->set_device_management_token(
         PolicyBuilder::kFakeToken);
     register_response_.mutable_register_response()->set_enrollment_type(
         em::DeviceRegisterResponse::ENTERPRISE);
     policy_fetch_response_.mutable_policy_response()->add_response()->CopyFrom(
         device_policy_.policy());
     robot_auth_fetch_response_.mutable_service_api_access_response()
         ->set_auth_code("auth_code_for_test");
@@ skipping 376 matching lines @@
                         DeviceCloudPolicyManagerChromeOSEnrollmentTest,
                         ::testing::Values(false, true));
 
 INSTANTIATE_TEST_CASE_P(
     Cert,
     DeviceCloudPolicyManagerChromeOSEnrollmentBlankSystemSaltTest,
     ::testing::Values(false, true));
 
 }  // namespace
 }  // namespace policy