Supervised User interstitial: Update strings to be more child-friendly

components/supervised_user_error_page/resources/supervised_user_block_interstitial.js

 // 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.
 
 function sendCommand(cmd) {
   window.domAutomationController.setAutomationId(1);
   window.domAutomationController.send(cmd);
 }
 
 function makeImageSet(url1x, url2x) {
@@ skipping 68 matching lines @@
     $('feedback').hidden = true;
   }
 }
 
 /**
  * Updates the interstitial to show that the request failed or was sent.
  * @param {boolean} isSuccessful Whether the request was successful or not.
  */
 function setRequestStatus(isSuccessful) {
   console.log('setRequestStatus(' + isSuccessful +')');
+  $('block-page-header').hidden = true;
   $('block-page-message').hidden = true;
   if (isSuccessful) {
     $('request-failed-message').hidden = true;
     $('request-sent-message').hidden = false;
     $('show-details-link').hidden = true;
     $('hide-details-link').hidden = true;
     $('details').hidden = true;
     $('back-button').hidden = !window.domAutomationController;
     $('request-access-button').hidden = true;
   } else {
     $('request-failed-message').hidden = false;
     $('request-access-button').hidden = false;
   }
 }
 
 document.addEventListener('DOMContentLoaded', initialize);