Extension Settings API: move the API functions into an object SettingsNamepace,

chrome/browser/extensions/settings/settings_storage_factory.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_SETTINGS_SETTINGS_STORAGE_FACTORY_H_
 #define CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_STORAGE_FACTORY_H_
 #pragma once
 
-class FilePath;
+#include <string>
+
+#include "base/file_path.h"
+#include "base/memory/ref_counted.h"
 
 namespace extensions {
 
 class SettingsStorage;
 
 // Factory for creating SettingStorage instances.
-class SettingsStorageFactory {
+//
+// Refcouted because it's just too messy to distribute these objects between
+// SettingsBackend instances any other way.
+class SettingsStorageFactory
+    : public base::RefCountedThreadSafe<SettingsStorageFactory> {
  public:
-  virtual ~SettingsStorageFactory() {}
-
-  // Create a new SettingsLeveldbStorage area.  Return NULL to indicate
-  // failure.  Must be called on the FILE thread.
+  // Creates a new SettingsStorage area for an extension under |base_path|.
+  // Return NULL to indicate failure.  Must be called on the FILE thread.
   virtual SettingsStorage* Create(
       const FilePath& base_path, const std::string& extension_id) = 0;
+
+ protected:
+  friend class base::RefCountedThreadSafe<SettingsStorageFactory>;
+  virtual ~SettingsStorageFactory() {}
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_STORAGE_FACTORY_H_