Design feedback: Destructive actions should warn user before completing

[TriVoxel]

I was able to click the "Delete Tab" button in this dialogue, and it immediately deleted the tab. If a user had important progress in the tab, such as many signed in accounts, locally saved draft data, etc, it could potentially lose someone a lot of time and progress.

Destructive actions such as deleting a tab, or #294 should prompt the user with a warning, asking if they are sure they meant to destroy their data. There's always a chance that someone in a hurry accidentally clicks this thinking it's a save button, or misclicks when editing their preferences, or is on a mobile phone with a cracked screen, and the screen registers random taps occasionally, etc.

Edit: As a side note, as per GNOME's design guidelines, destructive actions should also provide a way to undo them. Perhaps instead of immediately deleting the data, internally the application can move the data into a sort of recycle bin. You can display a toast to the user with a short message and undo button to revert the action. If the user closes the toast, the application can then delete the data for good. This would be a slightly more complex solution, but would be simple for the user and some users might find it useful.