[MD History] Disable Clear Browsing Data button for supervised users.

chrome/browser/resources/md_history/history_toolbar.js

 // Copyright 2015 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.
 
 Polymer({
   is: 'history-toolbar',
   properties: {
     // Number of history items currently selected.
     // TODO(calamity): bind this to
     // listContainer.selectedItem.selectedPaths.length.
@@ skipping 160 matching lines @@
   /** @private */
   onClearSelectionTap_: function() {
     this.fire('unselect-all');
   },
 
   /** @private */
   onDeleteTap_: function() {
     this.fire('delete-selected');
   },
 
-  /**
-   * If the user is a supervised user the delete button is not shown.
-   * @private
-   */
-  deletingAllowed_: function() {
-    return loadTimeData.getBoolean('allowDeletingHistory');
-  },
-
   /** @private */
   numberOfItemsSelected_: function(count) {
     return count > 0 ? loadTimeData.getStringF('itemsSelected', count) : '';
   },
 });