Implement an initial extension settings API.

chrome/browser/extensions/extension_settings.h

+// Copyright (c) 2011 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_EXTENSION_SETTINGS_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_
+#pragma once
+
+#include "base/callback.h"
+#include "base/file_path.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+
+// Manages ExtensionSettingsStorage objects for extensions.
+class ExtensionSettings {
+ public:
+  // File path is the base of the extension settings directory.
+  // The databases will be at base_path/extension_id.
+  explicit ExtensionSettings(const FilePath& base_path);
+  ~ExtensionSettings();
+
+  // Callback from the GetStorage() methods.
+  typedef base::Callback<void(ExtensionSettingsStorage*)> Callback;
+
+  // Gets the storage area for a given extension.
+  // By default this will be of a cached LEVELDB storage, but on failure to
+  // create a leveldb instance will fall back to cached NOOP storage.
+  // Callbacks will happen asynchronously regardless of whether they need to go
+  // to the FILE thread, but will always be called on the UI thread.
+  void GetStorage(const std::string& extension_id, const Callback& callback);
+
+  // Gets a storage area for a given extension with a specific type.
+  // and whether it should be wrapped in a cache.
+  // Use this for testing; if the given type fails to be created (e.g. if
+  // leveldb creation fails) then a DCHECK will fail.
+  // Callback objects will be deleted when used.
+  void GetStorageForTesting(
+      ExtensionSettingsStorage::Type type,
+      bool cached,
+      const std::string& extension_id,
+      const Callback& callback);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ExtensionSettings);
+
+  // Attempts to get and callback with an existing storage area.  Returns
+  // whether storage existed and the callback run.
+  bool GetExistingStorage(
+      const std::string& extension_id, const Callback& callback);
+
+  const FilePath base_path_;
+  std::map<std::string, ExtensionSettingsStorage*> storage_objs_;
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_