MD History: Show 'no synced tabs' when tab sync is disabled

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.
 
 Polymer({
   is: 'history-app',
 
   properties: {
     showSidebarFooter: Boolean,
 
@@ skipping 182 matching lines @@
     if (e.command.id == 'delete-command')
       this.deleteSelected();
   },
 
   /**
    * @param {!Array<!ForeignSession>} sessionList Array of objects describing
    *     the sessions from other devices.
    * @param {boolean} isTabSyncEnabled Is tab sync enabled for this profile?
    */
   setForeignSessions: function(sessionList, isTabSyncEnabled) {
-    if (!isTabSyncEnabled)
+    if (!isTabSyncEnabled) {
+      var syncedDeviceManagerElem =
+      /** @type {HistorySyncedDeviceManagerElement} */this
+          .$$('history-synced-device-manager');
+      if (syncedDeviceManagerElem)
+        syncedDeviceManagerElem.tabSyncDisabled();
       return;
+    }
 
     this.set('queryResult_.sessionList', sessionList);
   },
 
   /**
    * Update sign in state of synced device manager after user logs in or out.
    * @param {boolean} isUserSignedIn
    */
   updateSignInState: function(isUserSignedIn) {
     var syncedDeviceManagerElem =
@@ skipping 54 matching lines @@
     return selectedPage;
   },
 
   /** @private */
   closeDrawer_: function() {
     var drawer = this.$$('#drawer');
     if (drawer)
       drawer.close();
   },
 });