Reproducible on: Firefox 43.0a1, Firefox 42.0a2 across all platforms STR 1.Launch Firefox with clean profile. 2.Click menu [≡] → select "Customize". 3.Drag an item from the palette and drop it onto the menu panel. 4.Click “Restore Defaults” button. 5.Exit Customize mode. 6.Disable e10s and restart the browser. 7.Enable back e10s and restart the browser. 8.Check in the Panel Menu for the Non e10s Window item. ER Non e10s Window item is successfully displayed in Panel Menu. AR Non e10s Window item does not appear in Panel Menu. It is displayed in Additional Tools and Features palette from Customize Mode. It is repositioned in the Panel Menu after the “Restore Defaults” button is actioned. See screenshot: http://i.imgur.com/ymw0s6D.jpg Additional notes: - This issue is reproducible on Firefox 43.0a1 (2015-08-27) and Firefox 42.0a2 (2015-08-27) under Windows 7 64-bit, Ubuntu 14.04 32-bit and Mac Os X 10.9.5. - This issue also reproduces on Firefox 40.0a1 (2015-05-01).
temp debug feature, not a blocker.