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/file_path.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+#include "third_party/leveldb/include/leveldb/db.h"
+
+// Manages ExtensionSettingsStorage objects for extensions.
+class ExtensionSettings {
+ public:
+  // File path is the base of the extensions directory.
+  // The databases will be at base_path/extension_id/settings.
+  explicit ExtensionSettings(const FilePath& base_path);
+  ~ExtensionSettings();
+
+  // Callback for the GetStorage() methods.  The callback will always be Run()
+  // from a PostMessage to the UI thread, even if the storage area is cached.
+  class Callback {
+   public:
+    virtual ~Callback() {}
+
+    // Called when the storage area is available.  Ownership of the object
+    // remains with the ExtensionSettings object.
+    virtual void Run(ExtensionSettingsStorage* storage) = 0;
+  };
+
+  // Gets the storage area for a given extension.
+  // By default this will be of type LEVELDB|CACHED, but on failure to create
+  // a leveldb instance will fall back to NOOP|CACHED.
+  // Callback objects will be deleted when used.
+  void GetStorage(const std::string& extension_id, Callback* callback);
+
+  // Gets a storage area for a given extension, with a specific type, either
+  // NOOP, LEVELDB, NOOP|CACHED, or LEVELDB|CACHED.
+  // 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(int type, const std::string& extension_id,
+      Callback* callback);
+
+ private:
+  // 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, Callback* callback);
+
+  const FilePath base_path_;
+  std::map<std::string, ExtensionSettingsStorage*> storage_objs_;
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_H_