MD History: add sign in promo in synced tabs when user isn't logged in

chrome/browser/resources/md_history/app.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.
 
 /**
  * @typedef {{querying: boolean,
  *            searchTerm: string,
  *            results: ?Array<!HistoryEntry>,
  *            info: ?HistoryQuery,
  *            incremental: boolean,
@@ skipping 207 matching lines @@
    * @return {string}
    */
   getSelectedPage: function(selectedPage, range) {
     if (selectedPage == 'history-list' && range != HistoryRange.ALL_TIME)
       return 'history-grouped-list';
 
     return selectedPage;
   },
 
   /**
+   * Update sign in state of synced device manager after user logs in or out.
+   * @param {boolean} isUserSignedIn
+   */
+  updateSignInState: function(isUserSignedIn) {
+    var syncedDeviceManagerElem =
+      /** @type {HistorySyncedDeviceManagerElement} */this
+          .$$('history-synced-device-manager');
+    syncedDeviceManagerElem.updateSignInState(isUserSignedIn);
+  },
+
+  /**
    * @param {string} selectedPage
    * @return {boolean}
    * @private
    */
   syncedTabsSelected_: function(selectedPage) {
     return selectedPage == 'history-synced-device-manager';
   },
 
   /**
    * @param {boolean} querying
    * @param {boolean} incremental
    * @param {string} searchTerm
    * @return {boolean} Whether a loading spinner should be shown (implies the
    *     backend is querying a new search term).
    * @private
    */
   shouldShowSpinner_: function(querying, incremental, searchTerm) {
     return querying && !incremental && searchTerm != '';
   }
 });