Pref service: add persistent pref store frontend and backend.

services/preferences/public/cpp/pref_store_client.h

Index: services/preferences/public/cpp/pref_store_client.h
diff --git a/services/preferences/public/cpp/pref_store_client.h b/services/preferences/public/cpp/pref_store_client.h
index adad0c2b189f58a7b27e025589ba93ebface6ca7..b4d8245110074c60ea26ad7a0fc26fe3a77758c4 100644
--- a/services/preferences/public/cpp/pref_store_client.h
+++ b/services/preferences/public/cpp/pref_store_client.h
@@ -5,15 +5,9 @@
 #ifndef SERVICES_PREFERENCES_PUBLIC_CPP_PREF_STORE_CLIENT_H_
 #define SERVICES_PREFERENCES_PUBLIC_CPP_PREF_STORE_CLIENT_H_
 
-#include <string>
-
 #include "base/macros.h"
-#include "base/observer_list.h"
-#include "base/values.h"
 #include "components/prefs/pref_store.h"
-#include "components/prefs/pref_value_map.h"
-#include "mojo/public/cpp/bindings/binding.h"
-#include "services/preferences/public/cpp/pref_store_manager_impl.h"
+#include "services/preferences/public/cpp/pref_store_client_mixin.h"
 #include "services/preferences/public/interfaces/preferences.mojom.h"
 
 namespace prefs {
@@ -25,39 +19,13 @@ namespace prefs {
 //
 // PrefStoreClient provides synchronous access to the preferences stored by the
 // backing store by caching them locally.
-class PrefStoreClient : public ::PrefStore, public mojom::PrefStoreObserver {
+class PrefStoreClient : public PrefStoreClientMixin<::PrefStore> {
  public:
   explicit PrefStoreClient(mojom::PrefStoreConnectionPtr connection);
 
-  // PrefStore:
-  void AddObserver(PrefStore::Observer* observer) override;
-  void RemoveObserver(PrefStore::Observer* observer) override;
-  bool HasObservers() const override;
-  bool IsInitializationComplete() const override;
-  bool GetValue(const std::string& key,
-                const base::Value** result) const override;
-  std::unique_ptr<base::DictionaryValue> GetValues() const override;
-
  private:
-  friend class PrefStoreClientTest;
-
   ~PrefStoreClient() override;
 
-  // prefs::mojom::PreferenceObserver:
-  void OnPrefChanged(const std::string& key,
-                     std::unique_ptr<base::Value> value) override;
-  void OnInitializationCompleted(bool succeeded) override;
-
-  // Cached preferences.
-  std::unique_ptr<base::DictionaryValue> cached_prefs_;
-
-  base::ObserverList<PrefStore::Observer, true> observers_;
-
-  // Has the PrefStore we're observing been initialized?
-  bool initialized_;
-
-  mojo::Binding<mojom::PrefStoreObserver> observer_binding_;
-
   DISALLOW_COPY_AND_ASSIGN(PrefStoreClient);
 };