ExtensionSystem cleanup part 2

apps/shell/browser/shell_extension_system_factory.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 APPS_SHELL_BROWSER_SHELL_EXTENSION_SYSTEM_FACTORY_H_
+#define APPS_SHELL_BROWSER_SHELL_EXTENSION_SYSTEM_FACTORY_H_
+
+#include "base/memory/singleton.h"
+#include "extensions/browser/extension_system_provider.h"
+
+namespace extensions {
+
+// A factory that provides ShellExtensionSystem for app_shell.
+class ShellExtensionSystemFactory : public ExtensionSystemProvider {
+ public:
+  // ExtensionSystemProvider implementation:
+  virtual ExtensionSystem* GetForBrowserContext(
+      content::BrowserContext* context) OVERRIDE;
+
+  static ShellExtensionSystemFactory* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<ShellExtensionSystemFactory>;
+
+  ShellExtensionSystemFactory();
+  virtual ~ShellExtensionSystemFactory();
+
+  // BrowserContextKeyedServiceFactory implementation:
+  virtual BrowserContextKeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const OVERRIDE;
+  virtual content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const OVERRIDE;
+  virtual bool ServiceIsCreatedWithBrowserContext() const OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(ShellExtensionSystemFactory);
+};
+
+}  // namespace extensions
+
+#endif  // APPS_SHELL_BROWSER_SHELL_EXTENSION_SYSTEM_FACTORY_H_