>>> STR_1: 1. Open many new tabs to cause overflow in tabs toolbar 2. Right-click on new tab button STR_2: 1. Open new Firefox window 2. Right-click on new tab button AR: STR_2 - context menu shows menuitem "Undo close tab". STR_1 - context menu doesn't show that item ER: Some consistency implemented by UX team(?!) Either X or Y: X) No "undo close tab" menuitem ever (for new tab button), like it was on good old Firefox 28 Y) "Undo close tab" should be always displayed in context menu of new tab button Note: This also happens with several other menuitems - it becomes obvious during the testing. This is a regression. Good old Firefox 28 is unaffected (has logical behavior), Firefox 49 is affected (has illogical behavior described above).
Build ID: 20170130030205 User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0 Reproducible on Windows 10 x64bit on the latest Firefox release 51.0.1, on the latest Nightly 54.0a1 and on Nightly 49.0a1.
Too late for firefox 52, mass-wontfix.