Pref service: expose all read-only PrefStores through Mojo

services/preferences/public/cpp/pref_store_impl.h

+// 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_PREF_STORE_IMPL_H_
+#define SERVICES_PREFERENCES_PUBLIC_CPP_PREF_STORE_IMPL_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "components/prefs/pref_store.h"
+#include "components/prefs/pref_value_store.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "services/preferences/public/interfaces/preferences.mojom.h"
+
+namespace prefs {
+
+// Wraps an actual PrefStore implementation and exposes it as a
+// mojom::PrefStore interface.
+class PrefStoreImpl : public ::PrefStore::Observer, public mojom::PrefStore {
+ public:
+  PrefStoreImpl(scoped_refptr<::PrefStore> pref_store,
+                mojom::PrefStoreRequest request);
+  ~PrefStoreImpl() override;
+
+  // The created instance is registered in and owned by the
+  // |mojom::PrefStoreRegistry|.
+  static std::unique_ptr<PrefStoreImpl> Create(
+      mojom::PrefStoreRegistryPtr registry_ptr,
+      scoped_refptr<::PrefStore> pref_store,
+      PrefValueStore::PrefStoreType type);
+
+ private:
+  // PrefStore::Observer:
+  void OnPrefValueChanged(const std::string& key) override;
+  void OnInitializationCompleted(bool succeeded) override;
+
+  // prefs::mojom::PrefStore:
+  void AddObserver(const AddObserverCallback& callback) override;
+
+  // The backing store we observer for changes.
+  scoped_refptr<::PrefStore> backing_pref_store_;
+
+  // Observers we notify when |backing_pref_store_| changes.
+  std::vector<mojom::PrefStoreObserverPtr> observers_;
+
+  // True when the |backing_pref_store_| is initialized, either because it was
+  // passed already initialized in the constructor or after
+  // OnInitializationCompleted was called.
+  bool backing_pref_store_initialized_;
+
+  mojo::Binding<mojom::PrefStore> binding_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefStoreImpl);
+};
+
+}  // namespace prefs
+
+#endif  // SERVICES_PREFERENCES_PUBLIC_CPP_PREF_STORE_IMPL_H_