Switch base::Value typemapping to be by value instead of by unique_ptr.

services/preferences/persistent_pref_store_impl.cc

Index: services/preferences/persistent_pref_store_impl.cc
diff --git a/services/preferences/persistent_pref_store_impl.cc b/services/preferences/persistent_pref_store_impl.cc
index 95930387654f5c875d845330787287e8bbb2b662..24272a9d1599c8745da4b0590a0596c1e0587b7d 100644
--- a/services/preferences/persistent_pref_store_impl.cc
+++ b/services/preferences/persistent_pref_store_impl.cc
@@ -42,8 +42,7 @@ class PersistentPrefStoreImpl::Connection : public mojom::PersistentPrefStore {
     for (const auto& update : updates) {
       if (base::ContainsKey(observed_keys_, update->key)) {
         filtered_updates.push_back(mojom::PrefUpdate::New(
-            update->key,
-            update->value ? update->value->CreateDeepCopy() : nullptr, 0));
+            update->key, update->value ? update->value : base::nullopt, 0));
       }
     }
     if (!filtered_updates.empty())
@@ -112,8 +111,9 @@ PersistentPrefStoreImpl::CreateConnection(ObservedPrefs observed_prefs) {
   auto* connection_ptr = connection.get();
   connections_.insert(std::make_pair(connection_ptr, std::move(connection)));
   return mojom::PersistentPrefStoreConnection::New(
-      mojom::PrefStoreConnection::New(std::move(observer_request),
-                                      backing_pref_store_->GetValues(), true),
+      mojom::PrefStoreConnection::New(
+          std::move(observer_request),
+          std::move(*backing_pref_store_->GetValues()), true),
       std::move(pref_store_ptr), backing_pref_store_->GetReadError(),
       backing_pref_store_->ReadOnly());
 }
@@ -134,8 +134,8 @@ void PersistentPrefStoreImpl::SetValues(
 
   for (auto& update : updates) {
     if (update->value) {
-      backing_pref_store_->SetValue(update->key, std::move(update->value),
-                                    update->flags);
+      backing_pref_store_->SetValue(
+          update->key, update->value->CreateDeepCopy(), update->flags);
     } else {
       backing_pref_store_->RemoveValue(update->key, update->flags);
     }