Prevent extension sideloading from Windows registry

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 2a4b8ee17dc812d40de4f7baa88122c8aa152526..7969b89bb3da22284d68c29dcd4943fe9e2ccc17 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4556,6 +4556,9 @@ Make sure you do not expose any sensitive information.
       <message name="IDS_EXTENSION_INSTALL_KIOSK_MODE_ONLY" desc="Error displayed during installation of an app with 'kiosk_only' attribute but user is not in ChromeOS kiosk mode.">
         App with 'kiosk_only' manifest attribute must be installed in ChromeOS kiosk mode.
       </message>
+      <message name="IDS_EXTENSION_INSTALL_DISALLOW_UNTRUSTED_EXTENSION" desc="Error displayed during installation of a side-loaded extension from an untrusted source.">
+        Cannot install untrusted extension with ID "<ph name="IMPORT_ID">$1<ex>aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</ex></ph>."

[Evan Stade, 2014/12/20 01:27:59]

It seems this is not used anywhere. Can it be removed?

+      </message>
       <message name="IDS_EXTENSION_OVERLAPPING_WEB_EXTENT" desc="Error message when a user tries to install an app with a web extent that overlaps another installed app.">
         Could not add application because it conflicts with "<ph name="APP_NAME">$1<ex>Google Mail</ex></ph>".
       </message>