Pref service: add persistent pref store frontend and backend.

services/preferences/public/cpp/persistent_pref_store_client.h

Index: services/preferences/public/cpp/persistent_pref_store_client.h
diff --git a/services/preferences/public/cpp/persistent_pref_store_client.h b/services/preferences/public/cpp/persistent_pref_store_client.h
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+++ b/services/preferences/public/cpp/persistent_pref_store_client.h
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+// 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.
+
+#ifndef SERVICES_PREFERENCES_PUBLIC_CPP_PERSISTENT_PREF_STORE_CLIENT_H_
+#define SERVICES_PREFERENCES_PUBLIC_CPP_PERSISTENT_PREF_STORE_CLIENT_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "components/prefs/persistent_pref_store.h"
+#include "services/preferences/public/cpp/pref_store_client_mixin.h"
+#include "services/preferences/public/interfaces/preferences.mojom.h"
+
+namespace base {
+class Value;
+class DictionaryValue;
+}
+
+namespace prefs {
+
+// An implementation of PersistentPrefStore backed by a
+// mojom::PersistentPrefStore and a mojom::PrefStoreObserver.
+class PersistentPrefStoreClient
+    : public PrefStoreClientMixin<PersistentPrefStore> {
+ public:
+  explicit PersistentPrefStoreClient(
+      mojom::PersistentPrefStoreConnectorPtr connector);
+
+  // WriteablePrefStore:
+  void SetValue(const std::string& key,
+                std::unique_ptr<base::Value> value,
+                uint32_t flags) override;
+  void RemoveValue(const std::string& key, uint32_t flags) override;
+  bool GetMutableValue(const std::string& key, base::Value** result) override;
+  void ReportValueChanged(const std::string& key, uint32_t flags) override;
+  void SetValueSilently(const std::string& key,
+                        std::unique_ptr<base::Value> value,
+                        uint32_t flags) override;
+
+  // PersistentPrefStore:
+  bool ReadOnly() const override;
+  PrefReadError GetReadError() const override;
+  PrefReadError ReadPrefs() override;
+  void ReadPrefsAsync(ReadErrorDelegate* error_delegate) override;
+  void CommitPendingWrite() override;
+  void SchedulePendingLossyWrites() override;
+  void ClearMutableValues() override;
+
+ protected:
+  // base::RefCounted<PrefStore>:
+  ~PersistentPrefStoreClient() override;
+
+ private:
+  void OnCreateComplete(PrefReadError read_error,
+                        bool read_only,
+                        std::unique_ptr<base::DictionaryValue> cached_prefs,
+                        mojom::PersistentPrefStorePtr pref_store,
+                        mojom::PrefStoreObserverRequest observer_request);
+
+  mojom::PersistentPrefStoreConnectorPtr connector_;
+  bool read_only_ = false;
+  PrefReadError read_error_ = PersistentPrefStore::PREF_READ_ERROR_NONE;
+  mojom::PersistentPrefStorePtr pref_store_;
+
+  std::unique_ptr<ReadErrorDelegate> error_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(PersistentPrefStoreClient);
+};
+
+}  // namespace prefs
+
+#endif  // SERVICES_PREFERENCES_PUBLIC_CPP_PERSISTENT_PREF_STORE_CLIENT_H_