cros: Show dircryto migration banner

chrome/app/chromeos_strings.grdp

Index: chrome/app/chromeos_strings.grdp
diff --git a/chrome/app/chromeos_strings.grdp b/chrome/app/chromeos_strings.grdp
index 680ad09dc2da512e2e2ec7313561da97a00dd383..90f4d9f43c88ffa8a967e4f8df92d2742faecd3d 100644
--- a/chrome/app/chromeos_strings.grdp
+++ b/chrome/app/chromeos_strings.grdp
@@ -2134,6 +2134,9 @@ Press any key to continue exploring.
   <message name="IDS_LOGIN_CAPTCHA_INSTRUCTIONS" desc="Explanatory message shown when the user must type letters shown in a captcha image to reauthenticate.">
     Type the characters you see in the picture below.
   </message>
+  <message name="IDS_LOGIN_NEEDS_DIRCRYPTO_MIGRATION_BANNER" desc="Banner text for users that need to migrate their data to use dircrypto.">
+    You've got a new critical update. Sign in to get started.
+  </message>
   <message name="IDS_OPTIONS_SETTINGS_SECONDARY_USER_BANNER" desc="Banner displayed in settings page when the user is secondary in a multi-profile session.">
     Some settings belonging to <ph name="PRIMARY_EMAIL">$1<ex>john@google.com</ex></ph> are being shared with you. These settings only affect your account when using multiple sign-in.
   </message>