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

chrome/browser/extensions/extension_system_impl.cc

Index: chrome/browser/extensions/extension_system_impl.cc
diff --git a/chrome/browser/extensions/extension_system_impl.cc b/chrome/browser/extensions/extension_system_impl.cc
index ab1c01436412fd8ab89ee83eb0409d2ba6c7548a..d15f0ec27437fd6a9cfbeefd4cfb19781b146f2a 100644
--- a/chrome/browser/extensions/extension_system_impl.cc
+++ b/chrome/browser/extensions/extension_system_impl.cc
@@ -66,7 +66,9 @@
 #include "chrome/browser/app_mode/app_mode_utils.h"
 #include "chrome/browser/chromeos/app_mode/kiosk_app_update_install_gate.h"
 #include "chrome/browser/chromeos/extensions/device_local_account_management_policy_provider.h"
+#include "chrome/browser/chromeos/extensions/signin_screen_policy_provider.h"
 #include "chrome/browser/chromeos/policy/device_local_account.h"
+#include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/login/login_state.h"
 #include "components/user_manager/user.h"
@@ -118,6 +120,10 @@ void ExtensionSystemImpl::Shared::InitPrefs() {
       profile_, store_factory_, ValueStoreFrontend::BackendType::RULES, false));
 
 #if defined(OS_CHROMEOS)
+  // We can not perform check for Signin Profile here, as it would result in
+  // recursive call upon creation of Signin Profile, so we will create
+  // SigninScreenPolicyProvider lazily in RegisterManagementPolicyProviders.
+
   const user_manager::User* user =
       user_manager::UserManager::Get()->GetActiveUser();
   policy::DeviceLocalAccount::Type device_local_account_type;
@@ -128,7 +134,7 @@ void ExtensionSystemImpl::Shared::InitPrefs() {
         new chromeos::DeviceLocalAccountManagementPolicyProvider(
             device_local_account_type));
   }
-#endif  // defined(OS_CHROMEOS)
+#endif
 }
 
 void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
@@ -137,10 +143,20 @@ void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
           ->GetProviders());
 
 #if defined(OS_CHROMEOS)
+  // Lazy creation of SigninScreenPolicyProvider.
+  if (!signin_screen_policy_provider_) {
+    if (chromeos::ProfileHelper::IsSigninProfile(profile_)) {
+      signin_screen_policy_provider_.reset(
+          new chromeos::SigninScreenPolicyProvider());
+    }
+  }
+
   if (device_local_account_management_policy_provider_) {
     management_policy_->RegisterProvider(
         device_local_account_management_policy_provider_.get());
   }
+  if (signin_screen_policy_provider_)
+    management_policy_->RegisterProvider(signin_screen_policy_provider_.get());
 #endif  // defined(OS_CHROMEOS)
 
   management_policy_->RegisterProvider(InstallVerifier::Get(profile_));