Make empty sign-in banner hidden to avoid blocking user removal button

ui/login/account_picker/md_user_pod_row.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.
  *
  * This is the stylesheet used by user pods row of account picker UI.
  */
 
 podrow {
   /* Temporarily disabled because animation interferes with updating screen's
    size. */
@@ skipping 619 matching lines @@
   position: absolute;
   z-index: 6;
 }
 
 .action-box-area.active ~ .action-box-menu {
   background-color: rgba(0, 0, 0, 0.8);
   border-radius: 2px;
   display: flex;
   flex-direction: column;
   font-size: 13px;
-  margin: 3px 0 0 12px;
+  margin: 10px 0 0 12px;
   width: 220px;
 }
 
 .action-box-area.active ~ .action-box-menu.left-edge-offset {
   left: 0 !important;
 }
 
 .action-box-area.active ~ .action-box-menu.right-edge-offset {
   right: 0 !important;
 }
@@ skipping 477 matching lines @@
 .small-pod.extra-small .small-pod-name {
   left: 76px;
   padding: 16px 0;
   width: 190px;
 }
 
 @keyframes switch-image {
   from { transform: rotate3d(0, 1, 0, 90deg); }
   to { transform: none; }
 }