Unrevert r141537: Add extensions::StateStore and use that instead of

chrome/browser/extensions/state_store.h

+// Copyright (c) 2012 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_STATE_STORE_H_
+#define CHROME_BROWSER_EXTENSIONS_STATE_STORE_H_
+#pragma once
+
+#include <set>
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/value_store/value_store_frontend.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+
+namespace extensions {
+
+// A storage area for per-extension state that needs to be persisted to disk.
+class StateStore
+    : public base::SupportsWeakPtr<StateStore>,
+      public content::NotificationObserver {
+ public:
+  typedef ValueStoreFrontend::ReadCallback ReadCallback;
+
+  StateStore(Profile* profile, const FilePath& db_path);
+  virtual ~StateStore();
+
+  // Register a key for removal upon extension install/uninstall. We remove
+  // for install to reset state when an extension upgrades.
+  void RegisterKey(const std::string& key);
+
+  // Get the value associated with the given extension and key, and pass
+  // it to |callback| asynchronously.
+  void GetExtensionValue(const std::string& extension_id,
+                         const std::string& key,
+                         ReadCallback callback);
+
+  // Sets a value for a given extension and key.
+  void SetExtensionValue(const std::string& extension_id,
+                         const std::string& key,
+                         scoped_ptr<base::Value> value);
+
+ private:
+  // content::NotificationObserver
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // The store that holds our key/values.
+  ValueStoreFrontend store_;
+
+  // List of all known keys. They will be cleared for each extension when it is
+  // (un)installed.
+  std::set<std::string> registered_keys_;
+
+  content::NotificationRegistrar registrar_;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_STATE_STORE_H_