Allow explicitly whitelisted apps/extensions in public sessions

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 d79b999381105d3c7443832847cd083307dbdddf..145bf482829f5ff03c2fd6089756e2c8c2d07418 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4409,6 +4409,9 @@ Make sure you do not expose any sensitive information.
       <message name="IDS_EXTENSION_CANT_INSTALL_POLICY_BLOCKED" desc="Error message when a user tries to install an extension that is blocked by administrator policy.">
         <ph name="EXTENSION_NAME">$1<ex>Google Talk</ex></ph> (extension ID "<ph name="EXTENSION_ID">$2<ex>nckgahadagoaajjgafhacjanaoiihapd</ex></ph>") is blocked by the administrator.
       </message>
+      <message name="IDS_EXTENSION_CANT_INSTALL_IN_PUBLIC_SESSION" 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 public session.">
+        <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 a public session.
+      </message>
       <message name="IDS_EXTENSION_CANT_MODIFY_POLICY_REQUIRED" desc="Error message when a user tries to remove or change an extension that is required by administrator policy.">
         The administrator of this machine requires <ph name="EXTENSION_NAME">$1<ex>Google Talk</ex></ph> to be installed. It cannot be removed or modified.
       </message>