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

chrome/browser/resources/md_history/app.js

Index: chrome/browser/resources/md_history/app.js
diff --git a/chrome/browser/resources/md_history/app.js b/chrome/browser/resources/md_history/app.js
index c762ac93767bb9f5f49ba32d41b5841e98f2aa4c..377e109db265b75d7df6176128798a0dc8c25f3b 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -225,6 +225,17 @@ Polymer({
   },
 
   /**
+   * 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