Use {To/From}JavaTime for policy timestamps

chrome/browser/policy/cloud/cloud_policy_invalidator.cc

Index: chrome/browser/policy/cloud/cloud_policy_invalidator.cc
diff --git a/chrome/browser/policy/cloud/cloud_policy_invalidator.cc b/chrome/browser/policy/cloud/cloud_policy_invalidator.cc
index f63060f205bae6a4094cea212fe70a6143d0f0da..71a376d42aa883983b218a7a6eda775777a700e4 100644
--- a/chrome/browser/policy/cloud/cloud_policy_invalidator.cc
+++ b/chrome/browser/policy/cloud/cloud_policy_invalidator.cc
@@ -391,8 +391,8 @@ bool CloudPolicyInvalidator::IsPolicyChanged(
 }
 
 bool CloudPolicyInvalidator::IsInvalidationExpired(int64_t version) {
-  base::Time last_fetch_time = base::Time::UnixEpoch() +
-      base::TimeDelta::FromMilliseconds(core_->store()->policy()->timestamp());
+  base::Time last_fetch_time =
+      base::Time::FromJavaTime(core_->store()->policy()->timestamp());
 
   // If the version is unknown, consider the invalidation invalid if the
   // policy was fetched very recently.