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

chrome/browser/resources/md_history/history_item.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.
 
 /**
  * @param {!Element} root
  * @param {?Element} boundary
  * @param {cr.ui.FocusRow.Delegate} delegate
  * @constructor
  * @extends {cr.ui.FocusRow}
@@ skipping 93 matching lines @@
       lastFocused: {
         type: Object,
         notify: true,
       },
 
       ironListTabIndex: {
         type: Number,
         observer: 'ironListTabIndexChanged_',
       },
 
+      selectionNotAllowed_: {
+        type: Boolean,
+        value: !loadTimeData.getBoolean('allowDeletingHistory'),
+      },
+
       hasTimeGap: Boolean,
 
       index: Number,
 
       numberOfItems: Number,
 
       // The path of this history item inside its parent.
       path: String,
 
       // Search term used to obtain this history-item.
@@ skipping 58 matching lines @@
      */
     onItemClick_: function(e) {
       for (var i = 0; i < e.path.length; i++) {
         var elem = e.path[i];
         if (elem.id != 'checkbox' &&
             (elem.nodeName == 'A' || elem.nodeName == 'BUTTON')) {
           return;
         }
       }
 
-      if (this.selectionNotAllowed_())
+      if (this.selectionNotAllowed_)
         return;
 
       this.$.checkbox.focus();
       this.fire('history-checkbox-select', {
         element: this,
         shiftKey: e.shiftKey,
       });
     },
 
     /**
@@ skipping 92 matching lines @@
     },
 
     /**
      * Set the favicon image, based on the URL of the history item.
      * @private
      */
     showIcon_: function() {
       this.$.icon.style.backgroundImage = cr.icon.getFavicon(this.item.url);
     },
 
-    selectionNotAllowed_: function() {
-      return !loadTimeData.getBoolean('allowDeletingHistory');
-    },
-
     /**
      * @param {number} numberOfItems The number of items in the card.
      * @param {string} historyDate Date of the current result.
      * @param {string} search The search term associated with these results.
      * @return {string} The title for this history card.
      * @private
      */
     cardTitle_: function(numberOfItems, historyDate, search) {
       if (!search)
         return this.item.dateRelativeDay;
@@ skipping 37 matching lines @@
    */
   HistoryItem.searchResultsTitle = function(numberOfResults, searchTerm) {
     var resultId = numberOfResults == 1 ? 'searchResult' : 'searchResults';
     return loadTimeData.getStringF(
         'foundSearchResults', numberOfResults, loadTimeData.getString(resultId),
         searchTerm);
   };
 
   return {HistoryItem: HistoryItem};
 });