Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/extensions/api/storage/local_storage_backend.h

+// Copyright 2014 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 CHROME_BROWSER_EXTENSIONS_API_STORAGE_LOCAL_STORAGE_BACKEND_H_
+#define CHROME_BROWSER_EXTENSIONS_API_STORAGE_LOCAL_STORAGE_BACKEND_H_
+
+#include <map>
+#include <string>
+
+#include "base/memory/linked_ptr.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/extensions/api/storage/settings_backend.h"
+#include "chrome/browser/extensions/api/storage/settings_storage_quota_enforcer.h"
+
+namespace base {
+class FilePath;
+}
+
+class ValueStore;
+
+namespace extensions {
+class SettingStorageFactory;
+
+class LocalStorageBackend : public SettingsBackend {
+ public:
+  LocalStorageBackend(
+      const scoped_refptr<SettingsStorageFactory>& storage_factory,
+      const base::FilePath& base_path,
+      const SettingsStorageQuotaEnforcer::Limits& quota);
+  virtual ~LocalStorageBackend();
+
+  // SettingsBackend implementation.
+  virtual ValueStore* GetStorage(const std::string& extension_id) OVERRIDE;
+  virtual void DeleteStorage(const std::string& extension_id) OVERRIDE;
+
+ private:
+  typedef std::map<std::string, linked_ptr<ValueStore> > StorageMap;
+
+  StorageMap storage_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(LocalStorageBackend);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_STORAGE_LOCAL_STORAGE_BACKEND_H_