Fix misplacement of signin overlay and critical update message banner

ui/login/account_picker/md_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 {
   margin-top: 16px;
   z-index: 1;
 }
 
 #signin-banner-container1 {
   height: 64px;
+  max-width: 450px;
   position: absolute;
-  width: 520px;
   z-index: 3;
 }
 
 #signin-banner-container2 {
   display: inline-block;
   position: relative;
 }
 
 html[dir=rtl] #signin-banner-container2 {
   left: -50%;
@@ skipping 66 matching lines @@
   background: linear-gradient(#4FC3F7, transparent);
   height: 112px;
   position: absolute;
   width: 100%;
   z-index: 2;
 }
 
 .small-pod-container-mask.rotate {
   transform: rotate(180deg);
 }