Supervised users: Use custodian avatar image(s) in the block interstitial if they're available.

chrome/browser/resources/supervised_user_block_interstitial.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. */
 body {
   background-color: rgb(230, 230, 230);
   font-family: Helvetica, Arial, sans-serif;
   font-size: 10pt;
   margin: 50px 40px 20px 40px;
   text-align: center;
 }
@@ skipping 10 matching lines @@
   border-bottom: 1px solid rgb(136, 136, 136);
   border-radius: 3px;
   box-shadow: 0 2px 2px rgb(170, 170, 170);
   color: black;
 }
 
 h1 {
   color: rgb(102, 102, 102);
   font-size: 1.3em;
   font-weight: normal;
-  margin: 10px 0 30px 0;
-}
-
-#request-sent-message {
-  margin-top: 40px;
+  margin: 5px 0 30px 0;
 }
 
 a {
   color: rgb(17, 85, 204);
   text-decoration: none;
 }
 
 .error-img {
   /* Can't access chrome:// urls from an untrusted renderer process, so embed
    * the resource manually. */
   -webkit-user-select: none;
   content: -webkit-image-set(
       url('../../app/theme/default_100_percent/common/error_managed_mode_blocked_page.png') 1x,
       url('../../app/theme/default_200_percent/common/error_managed_mode_blocked_page.png') 2x);
-  margin-bottom: 10px;
+  margin-bottom: 15px;
   margin-top: 10px;
 }
 
+.avatar-container {
+  position: relative;
+}
+
+.avatar-img {
+  -webkit-user-select: none;
+  border: 3px solid rgb(251, 251, 251);
+  border-radius: 50%;
+  margin-bottom: 5px;
+  margin-top: 10px;
+  position: relative;
+}
+
 #content-top {
   margin: 20px 25px;
 }
 
 button {
   -webkit-user-select: none;
   background-image: linear-gradient(rgb(246, 246, 246) 5%,
                                     rgb(239, 239, 239) 50%,
                                     rgb(221, 221, 221));
   border: 1px solid rgb(209, 209, 211);
@@ skipping 22 matching lines @@
   #back-button {
     width: 100px;
   }
 }
 
 @media (max-width: 375px) {
   button {
     width: 100%;
   }
 }