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

services/preferences/public/cpp/pref_store_client_mixin.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/pref_store_client_mixin.h"
 
 #include <utility>
 
 #include "base/values.h"
 #include "services/preferences/public/cpp/pref_store_client.h"
@@ skipping 41 matching lines @@
   DCHECK(initialized_);
   DCHECK(cached_prefs_);
   return cached_prefs_->CreateDeepCopy();
 }
 
 template <typename BasePrefStore>
 PrefStoreClientMixin<BasePrefStore>::~PrefStoreClientMixin() = default;
 
 template <typename BasePrefStore>
 void PrefStoreClientMixin<BasePrefStore>::Init(
-    std::unique_ptr<base::DictionaryValue> initial_prefs,
+    const base::DictionaryValue* initial_prefs,
     bool initialized,
     mojom::PrefStoreObserverRequest observer_request) {
-  cached_prefs_ = std::move(initial_prefs);
+  if (initial_prefs)
+    cached_prefs_ = initial_prefs->CreateDeepCopy();
   observer_binding_.Bind(std::move(observer_request));
   if (initialized)
     OnInitializationCompleted(static_cast<bool>(cached_prefs_));
 }
 
 template <typename BasePrefStore>
 base::DictionaryValue& PrefStoreClientMixin<BasePrefStore>::GetMutableValues() {
   DCHECK(cached_prefs_);
   return *cached_prefs_;
 }
@@ skipping 18 matching lines @@
   if (!initialized_) {
     initialized_ = true;
     for (auto& observer : observers_)
       observer.OnInitializationCompleted(succeeded);
   }
 }
 
 template <typename BasePrefStore>
 void PrefStoreClientMixin<BasePrefStore>::OnPrefChanged(
     const std::string& key,
-    std::unique_ptr<base::Value> value) {
+    base::Optional<base::Value> value) {
   DCHECK(cached_prefs_);
   bool changed = false;
   if (!value) {  // Delete
     if (cached_prefs_->RemovePath(key, nullptr))
       changed = true;
   } else {
     const base::Value* prev;
     if (cached_prefs_->Get(key, &prev)) {
-      if (!prev->Equals(value.get())) {
-        cached_prefs_->Set(key, std::move(value));
+      if (*prev != *value) {
+        cached_prefs_->Set(key, value->CreateDeepCopy());
         changed = true;
       }
     } else {
-      cached_prefs_->Set(key, std::move(value));
+      cached_prefs_->Set(key, value->CreateDeepCopy());
       changed = true;
     }
   }
   if (changed && initialized_)
     ReportPrefValueChanged(key);
 }
 
 template class PrefStoreClientMixin<::PrefStore>;
 template class PrefStoreClientMixin<::PersistentPrefStore>;
 
 }  // namespace prefs