cros: Show dircryto migration banner

ui/login/account_picker/screen_account_picker.css

 /* Copyright 2014 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 .account-picker.flying-pods #account-picker {
   transition: width 180ms ease, height 180ms ease;
 }
 
 #bubble {
@@ skipping 33 matching lines @@
 
 html[dir=rtl] #signin-banner {
   left: auto;
   right: -50%;
 }
 
 html[screen=user-adding] #signin-banner {
   display: inline-block;
 }
 
+html[screen=login] #signin-banner,
 html[screen=lock] #signin-banner {
   display: inline-block;
   opacity: 0;
   visibility: hidden;
 }
 
+html[screen=login] #signin-banner.message-set,
 html[screen=lock] #signin-banner.message-set {
   opacity: 1;
   transition: opacity 1s;
   visibility: visible;
 }