Add policy provider that would filter extensions/apps allowed on the

chrome/browser/extensions/extension_system_impl.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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_IMPL_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_IMPL_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/common/one_shot_event.h"
 
 class Profile;
 class ValueStore;
 
+#if defined(OS_CHROMEOS)
+namespace chromeos {
+class DeviceLocalAccountManagementPolicyProvider;
+class SigninScreenPolicyProvider;
+}
+#endif  // defined(OS_CHROMEOS)
+
 namespace extensions {
 
 class ExtensionSystemSharedFactory;
 class NavigationObserver;
 class StateStoreNotificationObserver;
 class UninstallPingSender;
 class InstallGate;
 class ValueStoreFactory;
 class ValueStoreFactoryImpl;
 
@@ skipping 99 matching lines @@
     std::unique_ptr<InstallGate> update_install_gate_;
 
     // For verifying the contents of extensions read from disk.
     scoped_refptr<ContentVerifier> content_verifier_;
 
     std::unique_ptr<UninstallPingSender> uninstall_ping_sender_;
 
 #if defined(OS_CHROMEOS)
     std::unique_ptr<chromeos::DeviceLocalAccountManagementPolicyProvider>
         device_local_account_management_policy_provider_;
+    std::unique_ptr<chromeos::SigninScreenPolicyProvider>
+        signin_screen_policy_provider_;
     std::unique_ptr<InstallGate> kiosk_app_update_install_gate_;
 #endif
 
     OneShotEvent ready_;
   };
 
   Profile* profile_;
 
   Shared* shared_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSystemImpl);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_IMPL_H_