Use {To/From}JavaTime for policy timestamps

components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc

Index: components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc
diff --git a/components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc b/components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc
index e891c3f9e39d03c49e8cf4ba3ed80bed1c33fd91..8f454d7f525b5b4dbad24bafa078deb87cdb7829 100644
--- a/components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc
+++ b/components/policy/core/common/cloud/component_cloud_policy_store_unittest.cc
@@ -175,7 +175,8 @@ TEST_F(ComponentCloudPolicyStoreTest, ValidatePolicyWrongTimestamp) {
   EXPECT_TRUE(store_->Store(kTestPolicyNS, CreateSerializedResponse(),
                             CreatePolicyData(), TestPolicyHash(), kTestPolicy));
 
-  const int64_t kPastTimestamp = base::TimeDelta::FromDays(1).InMilliseconds();
+  const int64_t kPastTimestamp =
+      (base::Time() + base::TimeDelta::FromDays(1)).ToJavaTime();
   CHECK_GT(ComponentPolicyBuilder::kFakeTimestamp, kPastTimestamp);
   builder_.policy_data().set_timestamp(kPastTimestamp);
   EXPECT_FALSE(store_->ValidatePolicy(kTestPolicyNS, CreateResponse(),
@@ -183,9 +184,8 @@ TEST_F(ComponentCloudPolicyStoreTest, ValidatePolicyWrongTimestamp) {
                                       nullptr /* payload */));
 
   const int64_t kFutureTimestamp =
-      (base::Time::NowFromSystemTime() + base::TimeDelta::FromDays(1) -
-       base::Time::UnixEpoch())
-          .InMilliseconds();
+      (base::Time::NowFromSystemTime() + base::TimeDelta::FromDays(1))
+          .ToJavaTime();
   builder_.policy_data().set_timestamp(kFutureTimestamp);
   EXPECT_FALSE(store_->ValidatePolicy(kTestPolicyNS, CreateResponse(),
                                       nullptr /* policy_data */,