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..a1be6d3ee7e5a386aad16456672fa4f8adfcaa15 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"
@@ -128,7 +130,10 @@ void ExtensionSystemImpl::Shared::InitPrefs() {
         new chromeos::DeviceLocalAccountManagementPolicyProvider(
             device_local_account_type));
   }
-#endif  // 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.
+#endif
 }
 
 void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
@@ -137,10 +142,21 @@ void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
           ->GetProviders());
 
 #if defined(OS_CHROMEOS)
+  // Lazy creation of SigninScreenPolicyProvider.
+  if (!signin_screen_policy_provider_) {
+    if (profile_ ==
+        chromeos::ProfileHelper::GetSigninProfile()->GetOriginalProfile()) {

[Devlin, 2016/11/11 16:35:08]

nit: prefer Profile::IsSameProfile()

[Denis Kuznetsov (DE-MUC), 2016/11/11 21:26:34]

Acknowledged.

+      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_));