open a sidebar, use the context menu. every item is enabled. console has: JavaScript error: resource:///modules/CustomizableUI.jsm, line 1368: Error: buildWidget was called for a non-browser window! JavaScript error: chrome://browser/content/webext-panels.xul?panel=moz-extension%3A%2F%2F37c1a7d0-db5c-c145-a851-61e5f37cf839%2Fpage.html&remote=1&browser-style=1, line 1: TypeError: gContextMenu is null

Comment on attachment 8889671 [details] Bug 1383908 check if we're running in a main window before using CUI, https://reviewboard.mozilla.org/r/160738/#review166264 ::: browser/base/content/browser-social.js:365 (Diff revision 1) > > get shareButton() { > // web-panels (bookmark/sidebar) don't include customizableui, so > // nsContextMenu fails when accessing shareButton, breaking > // browser_bug409481.js. > - if (!window.CustomizableUI) > + if (document.documentElement.getAttribute("id") !== "main-window") Please check `document.documentElement.getAttribute("windowtype")` against `navigator:browser` instead. With that, r=me.

Pushed by mixedpuppy@gmail.com: https://hg.mozilla.org/integration/autoland/rev/39b5cf816c13 check if we're running in a main window before using CUI, r=Gijs