In Firefox Android: Click tab icon (which shows how many tabs you have open) -> click menu. You have two options: 'New Private Tab' or 'Close All Tabs'. If you click 'Close All Tabs' by accident (they're right next to each other), there's no confirmation. I know there's a 'recently closed tabs' section on the History page, but that only shows a max of 10 tabs - with no way to retrieve any of the older tabs. Might it be useful to get user confirmation when they try to close all tabs?