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

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 5591614230235544513cd2d80306b368d76ea307..e94831295d8d5567212d634adaccccac2e42ad06 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4124,6 +4124,9 @@ Even if you have downloaded files from this website before, the website might ha
         <message name="IDS_EXTENSION_CANT_INSTALL_IN_DEVICE_LOCAL_ACCOUNT" desc="Error message when a user tries to install or the administrator tries to force-install through policy an extension that is not allowed in a device-local account.">
           <ph name="EXTENSION_NAME">$1<ex>Google Talk</ex></ph> (extension ID "<ph name="EXTENSION_ID">$2<ex>nckgahadagoaajjgafhacjanaoiihapd</ex></ph>") is not allowed in this type of session.
         </message>
+        <message name="IDS_EXTENSION_CANT_INSTALL_ON_LOGIN_SCREEN" desc="Error message when the administrator tries to force-install through policy an extension that is not allowed on a local screen.">
+          <ph name="EXTENSION_NAME">$1<ex>Google Talk</ex></ph> (extension ID "<ph name="EXTENSION_ID">$2<ex>nckgahadagoaajjgafhacjanaoiihapd</ex></ph>") is not allowed on a login screen.
+        </message>
       </if>
       <message name="IDS_EXTENSION_MOVE_DIRECTORY_TO_PROFILE_FAILED" desc="">
         Could not move extension directory into profile.