MD History: Update sign in state in data source

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 33e2c62d79a61eec7d0d97c1c32fad400fe67ff8..850249d40ed8ab96975e93a83a71e088d86edd57 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -22,7 +22,10 @@ cr.define('md_history', function() {
 Polymer({
   is: 'history-app',
 
-  behaviors: [Polymer.IronScrollTargetBehavior],
+  behaviors: [
+    Polymer.IronScrollTargetBehavior,
+    WebUIListenerBehavior,
+  ],
 
   properties: {
     // Used to display notices for profile sign-in status.
@@ -74,8 +77,7 @@ Polymer({
 
     isUserSignedIn_: {
       type: Boolean,
-      // Updated on synced-device-manager attach by chrome.sending
-      // 'otherDevicesInitialized'.
+      // Updated on synced-device-manager.
       value: loadTimeData.getBoolean('isUserSignedIn'),
     },
 
@@ -105,6 +107,12 @@ Polymer({
     document.addEventListener('command', this.onCommand_.bind(this));
   },
 
+  /** @override */
+  attached: function() {
+    this.addWebUIListener('sign-in-state-updated',
+                          this.updateSignInState.bind(this));

[Dan Beam, 2016/09/28 03:56:49]

this part is perfect :)

+  },
+
   onFirstRender: function() {
     setTimeout(function() {
       chrome.send(