MD History: Get sign in state from backend when refreshing the page

chrome/browser/resources/md_history/synced_device_manager.js

Index: chrome/browser/resources/md_history/synced_device_manager.js
diff --git a/chrome/browser/resources/md_history/synced_device_manager.js b/chrome/browser/resources/md_history/synced_device_manager.js
index 2a776551cb17ab22270d755a8f8581c6a89edaaa..63946e1c7730b90e5761f0935d0dd71252b485f2 100644
--- a/chrome/browser/resources/md_history/synced_device_manager.js
+++ b/chrome/browser/resources/md_history/synced_device_manager.js
@@ -41,7 +41,7 @@ Polymer({
     /** @private */
     signInState_: {
       type: Boolean,
-      value: loadTimeData.getBoolean('isUserSignedIn'),
+      value: true,

[calamity, 2016/07/29 05:14:59]

You might want to leave this in... I think this will be janky with non-signed in
profiles if you go directly to chrome://history/syncedTabs.

[lshang, 2016/07/29 06:11:58]

Done.

     },
 
     /** @private */
@@ -57,6 +57,15 @@ Polymer({
     }
   },
 
+  /** @override */
+  attached: function() {
+    // When user signs in or out with MD History tab open, the internal sign in
+    // state will be updated, but refreshing the page will still get the
+    // outdated state. Get the current state from backend when element is
+    // attached.
+    this.getSignInState_();

[calamity, 2016/07/29 05:14:59]

No need for a method here, just chrome.send('otherDevicesInitialized').

The comment // Update the sign in state. is probably sufficient. The current
comment is a bit too specific.

[lshang, 2016/07/29 06:11:58]

Done.

+  },
+
   /**
    * @param {!ForeignSession} session
    * @return {!ForeignDeviceInternal}
@@ -103,6 +112,10 @@ Polymer({
     };
   },
 
+  /** @private */
+  getSignInState_: function() {
+    chrome.send('getSignInState');
+  },
 
   onSignInTap_: function() {
     chrome.send('SyncSetupShowSetupUI');