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

services/preferences/public/cpp/persistent_pref_store_client.cc

 // Copyright 2017 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 "services/preferences/public/cpp/persistent_pref_store_client.h"
 
 #include <utility>
 
 #include "base/values.h"
 #include "components/prefs/pref_registry.h"
@@ skipping 128 matching lines @@
         other_pref_stores) {
   connector_.reset();
   read_error_ = connection->read_error;
   read_only_ = connection->read_only;
   pref_store_ = std::move(connection->pref_store);
   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
     error_delegate_->OnError(read_error_);
   error_delegate_.reset();
 
   if (connection->pref_store_connection) {
-    Init(std::move(connection->pref_store_connection->initial_prefs), true,
+    Init(&connection->pref_store_connection->initial_prefs, true,
          std::move(connection->pref_store_connection->observer));
   } else {
     Init(nullptr, false, nullptr);
   }
 }
 
 void PersistentPrefStoreClient::QueueWrite(const std::string& key,
                                            uint32_t flags) {
   if (pending_writes_.empty()) {
     // Use a weak pointer since a pending write should not prolong the life of
     // |this|. Instead, the destruction of |this| will flush any pending writes.
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(&PersistentPrefStoreClient::FlushPendingWrites,
                               weak_factory_.GetWeakPtr()));
   }
   pending_writes_.insert(std::make_pair(key, flags));
 }
 
 void PersistentPrefStoreClient::FlushPendingWrites() {
   std::vector<mojom::PrefUpdatePtr> updates;
   for (const auto& pref : pending_writes_) {
     const base::Value* value = nullptr;
     if (GetValue(pref.first, &value)) {
-      updates.push_back(mojom::PrefUpdate::New(
-          pref.first, value->CreateDeepCopy(), pref.second));
+      updates.push_back(
+          mojom::PrefUpdate::New(pref.first, *value, pref.second));
     } else {
       updates.push_back(
-          mojom::PrefUpdate::New(pref.first, nullptr, pref.second));
+          mojom::PrefUpdate::New(pref.first, base::nullopt, pref.second));
     }
   }
   pref_store_->SetValues(std::move(updates));
   pending_writes_.clear();
 }
 
 }  // namespace prefs