Hide the "downloads" page policy disabled UI elements from supervised users

chrome/browser/resources/downloads/downloads.js

 // Copyright (c) 2012 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.
 
 // TODO(jhawkins): Use hidden instead of showInline* and display:none.
 
 /**
  * Sets the display style of a node.
  * @param {!Element} node The target element to show or hide.
  * @param {boolean} isShow Should the target element be visible.
@@ skipping 321 matching lines @@
     this.controlRemove_ = createLink(this.remove_.bind(this),
         loadTimeData.getString('control_removefromlist'));
     this.controlRemove_.classList.add('control-remove-link');
   } else {
     this.controlRemove_ = document.createElement('span');
     this.controlRemove_.classList.add('disabled-link');
     var text = document.createTextNode(
         loadTimeData.getString('control_removefromlist'));
     this.controlRemove_.appendChild(text);
   }
+  if (!loadTimeData.getBoolean('show_delete_history'))
+    this.controlRemove_.hidden = true;
+
   this.nodeControls_.appendChild(this.controlRemove_);
 
   this.controlCancel_ = createLink(this.cancel_.bind(this),
       loadTimeData.getString('control_cancel'));
   this.nodeControls_.appendChild(this.controlCancel_);
 
   this.controlByExtension_ = document.createElement('span');
   this.nodeControls_.appendChild(this.controlByExtension_);
 
   // Container for 'unsafe download' UI.
@@ skipping 374 matching lines @@
   var clearAllElement;
   if (loadTimeData.getBoolean('allow_deleting_history')) {
     clearAllElement = createLink(clearAll, loadTimeData.getString('clear_all'));
     clearAllElement.classList.add('clear-all-link');
     clearAllHolder.classList.remove('disabled-link');
   } else {
     clearAllElement = document.createTextNode(
         loadTimeData.getString('clear_all'));
     clearAllHolder.classList.add('disabled-link');
   }
+  if (!loadTimeData.getBoolean('show_delete_history'))
+    clearAllHolder.hidden = true;
+
   clearAllHolder.appendChild(clearAllElement);
   clearAllElement.oncontextmenu = function() { return false; };
 
   // TODO(jhawkins): Use a link-button here.
   var openDownloadsFolderLink = $('open-downloads-folder');
   openDownloadsFolderLink.onclick = function() {
     chrome.send('openDownloadsFolder');
   };
   openDownloadsFolderLink.oncontextmenu = function() { return false; };
 
@@ skipping 81 matching lines @@
     if (Date.now() - start > 50) {
       clearTimeout(resultsTimeout);
       resultsTimeout = setTimeout(tryDownloadUpdatedPeriodically, 5);
       break;
     }
   }
 }
 
 // Add handlers to HTML elements.
 window.addEventListener('DOMContentLoaded', load);