Pref service: add persistent pref store frontend and backend.

services/preferences/public/cpp/pref_store_client_mixin.cc

Index: services/preferences/public/cpp/pref_store_client_mixin.cc
diff --git a/services/preferences/public/cpp/pref_store_client_mixin.cc b/services/preferences/public/cpp/pref_store_client_mixin.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f9766c91f8f8f1bd2ef9bf443596da00489aff0c
--- /dev/null
+++ b/services/preferences/public/cpp/pref_store_client_mixin.cc
@@ -0,0 +1,122 @@
+// 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"
+
+namespace prefs {
+
+template <typename BasePrefStore>
+PrefStoreClientMixin<BasePrefStore>::PrefStoreClientMixin()
+    : observer_binding_(this) {}
+
+template <typename BasePrefStore>
+void PrefStoreClientMixin<BasePrefStore>::AddObserver(
+    PrefStore::Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+template <typename BasePrefStore>
+void PrefStoreClientMixin<BasePrefStore>::RemoveObserver(
+    PrefStore::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+template <typename BasePrefStore>
+bool PrefStoreClientMixin<BasePrefStore>::HasObservers() const {
+  return observers_.might_have_observers();
+}
+
+template <typename BasePrefStore>
+bool PrefStoreClientMixin<BasePrefStore>::IsInitializationComplete() const {
+  return initialized_ && static_cast<bool>(cached_prefs_);
+}
+
+template <typename BasePrefStore>
+bool PrefStoreClientMixin<BasePrefStore>::GetValue(
+    const std::string& key,
+    const base::Value** result) const {
+  DCHECK(initialized_);
+  DCHECK(cached_prefs_);
+  return cached_prefs_->Get(key, result);
+}
+
+template <typename BasePrefStore>
+std::unique_ptr<base::DictionaryValue>
+PrefStoreClientMixin<BasePrefStore>::GetValues() const {
+  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,
+    bool initialized,
+    mojom::PrefStoreObserverRequest observer_request) {
+  cached_prefs_ = std::move(initial_prefs);
+  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_;
+}
+
+template <typename BasePrefStore>
+void PrefStoreClientMixin<BasePrefStore>::ReportPrefValueChanged(
+    const std::string& key) {
+  for (auto& observer : observers_)
+    observer.OnPrefValueChanged(key);
+}
+
+template <typename BasePrefStore>
+void PrefStoreClientMixin<BasePrefStore>::OnPrefChanged(
+    const std::string& key,
+    std::unique_ptr<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));
+        changed = true;
+      }
+    } else {
+      cached_prefs_->Set(key, std::move(value));
+      changed = true;
+    }
+  }
+  if (changed)
+    ReportPrefValueChanged(key);
+}
+
+template <typename BasePrefStore>
+void PrefStoreClientMixin<BasePrefStore>::OnInitializationCompleted(
+    bool succeeded) {
+  if (!initialized_) {
+    initialized_ = true;
+    for (auto& observer : observers_)
+      observer.OnInitializationCompleted(succeeded);
+  }
+}
+
+template class PrefStoreClientMixin<::PrefStore>;
+template class PrefStoreClientMixin<::PersistentPrefStore>;
+
+}  // namespace prefs