Desktop error bubble should be yellow.

ui/login/bubble.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.
  *
  * Css based bubble.
  */
 
 .bubble {
   background: rgba(0, 0, 0, 0.8);
   border-radius: 2px;
   box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
   color: rgba(255, 255, 255, 0.87);
   font-size: 12px;
   margin: 2px;
   max-width: 250px;
   padding: 8px;
   position: absolute;
   transition: opacity 200ms ease-in-out;
 }
 
+body.chromeos .bubble {
+  padding: 16px;
+}
+
 /* --- oldstyle begin --- */
 
 .bubble[oldstyle] {
   background: white;
   border: 1px solid rgba(0, 0, 0, 0.25);
   color: unset;
 }
 
 .bubble[oldstyle]::before {
   border-style: solid;
@@ skipping 86 matching lines @@
 
 html[dir=ltr] .bubble-left::after,
 html[dir=rtl] .bubble-right::after {
   border-color: transparent transparent transparent white;
   right: -15px;
   top: 17px;
 }
 
 /* --- oldstyle end --- */
 
-.error-message-bubble::before {
+body.chromeos .error-message-bubble::before {
   -webkit-mask-image: url(../../ui/webui/resources/images/warning.svg);
   -webkit-mask-position: left top;
   -webkit-mask-repeat: no-repeat;
   -webkit-mask-size: 20px;
   background-color: rgb(255,255,255);
   content: '';
   display: block;
   height: 20px;
   left: 8px;
   position: absolute;
   top: 8px;
   width: 20px;
 }
 
-.error-message-bubble {
+body:not(.chromeos) .error-message-bubble {
+  -webkit-padding-start: 30px;
+  background: url(chrome://theme/IDR_WARNING) left top no-repeat;
+  background-size: 24px;
+}
+
+body.chromeos .error-message-bubble {
   -webkit-padding-start: 20px;
 }
 
 .bubble[match-width] .error-message-bubble {
   -webkit-padding-start: unset;
   padding-top: 20px;
 }
 
-.bubble a {
+body.chromeos .bubble a {
   color: #7baaf7;
   text-decoration: none;
 }
 
 .error-message-bubble-padding {
   margin-bottom: 10px;
 }
 
 html[dir=rtl] .error-message-bubble {
   background-position: right top;
 }