Disable Clear Browsing Data button in History for guest profiles

chrome/browser/resources/md_history/side_bar.js

 // Copyright 2016 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-side-bar',
 
   behaviors: [Polymer.IronA11yKeysBehavior],
 
   properties: {
     selectedPage: {
       type: String,
       notify: true,
     },
 
+    /** @private */
+    guestSession_: {
+      type: Boolean,
+      value: loadTimeData.getBoolean('isGuestSession'),
+    },
+
     showFooter: Boolean,
   },
 
   keyBindings: {
     'space:keydown': 'onSpacePressed_',
   },
 
   /**
    * @param {CustomEvent} e
    * @private
@@ skipping 16 matching lines @@
    */
   onClearBrowsingDataTap_: function(e) {
     var browserService = md_history.BrowserService.getInstance();
     browserService.recordAction('InitClearBrowsingData');
     browserService.openClearBrowsingData();
     /** @type {PaperRippleElement} */ (this.$['cbd-ripple']).upAction();
     e.preventDefault();
   },
 
   /**
+   * @return {number}
+   * @private
+   */
+  computeClearBrowsingDataTabIndex_: function() {
+    return this.guestSession_ ? -1 : 0;
+  },
+
+  /**
    * Prevent clicks on sidebar items from navigating. These are only links for
    * accessibility purposes, taps are handled separately by <iron-selector>.
    * @private
    */
   onItemClick_: function(e) {
     e.preventDefault();
   },
 });