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 93f805653292a613e3cc88f2c9e31bbb1b6a2616..12eb840794e532a9f5481baa3160f5a5fdb87853 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -222,6 +222,19 @@ 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');
+    waitForUpgrade(syncedDeviceManagerElem).then(function() {

[tsergeant, 2016/06/17 06:22:02]

There's no need to use waitForUpgrade here.

That's only necessary in history.js, which runs before Polymer has started.

In app.js (a polymer file), all the child elements of <history-app> will always
be initialized (with one or two exceptions).

[lshang, 2016/06/21 03:00:26]

Done.

+      syncedDeviceManagerElem.updateSignInState(isUserSignedIn);
+    });
+  },
+
+  /**
    * @param {string} selectedPage
    * @return {boolean}
    * @private