Use hidden attribute rather the 'display: none' for hiding menus.

chrome/browser/resources/ntp4/other_sessions.js

Index: chrome/browser/resources/ntp4/other_sessions.js
diff --git a/chrome/browser/resources/ntp4/other_sessions.js b/chrome/browser/resources/ntp4/other_sessions.js
index 5e38764bdb7bf369c32ba4276b8e2040222189be..1a0f60d9a221e9cc10fa98e1d55349b1165562b3 100644
--- a/chrome/browser/resources/ntp4/other_sessions.js
+++ b/chrome/browser/resources/ntp4/other_sessions.js
@@ -55,7 +55,6 @@ cr.define('ntp', function() {
       // Create the context menu that appears when the user right clicks
       // on a device name.
       this.deviceContextMenu_ = DeviceContextMenuController.getInstance().menu;
-      this.deviceContextMenu_.style.display = 'none';
       document.body.appendChild(this.deviceContextMenu_);
 
       this.promoMessage_ = $('other-sessions-promo-template').cloneNode(true);
@@ -107,7 +106,7 @@ cr.define('ntp', function() {
      */
     hideMenu: function() {
       // Don't hide if the device context menu is currently showing.
-      if (this.deviceContextMenu_.style.display == 'none')
+      if (this.deviceContextMenu_.hidden)
         MenuButton.prototype.hideMenu.call(this);
     },