Fix avatar image size in user pods on desktop

ui/login/account_picker/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 65 matching lines @@
 .user-image-container {
   align-items: center;
   display: flex;
   height: 100%;
   justify-content: center;
   width: 100%;
 }
 
 .pod .user-image {
   flex: none;
+}
+
+/* TODO(noms): Refactor this out into a CrOS-specific file and simplify the
+ style rule once it is included on CrOS only. crbug.com/397638 */
+html:not([screen=login-add-user]) .pod .user-image {
   max-height: 160px;
   max-width: 160px;
   opacity: 0.7;
 }
 
-.pod.focused .user-image {
+html:not([screen=login-add-user]) .pod.focused .user-image {
   opacity: 1;
 }
 
 .pod.multiprofiles-policy-applied .user-image {
   -webkit-filter: grayscale(100%);
 }
 
 .signed-in-indicator {
   display: none;
 }
@@ skipping 469 matching lines @@
   top: 4px;
 }
 
 .pod.public-account.expanded.advanced .language-and-input-container {
   display: none;
 }
 
 .enter-button {
   font-size: 14px;
 }