Use tabId parameter to set badge text specifically for each window

[nt1m]

You can use the tabId parameter of setBadgeText() to set a different badge text per-window.

[Timvde]

I know. I have been looking into doing this, but it turned out to be hard to manage when switching tabs in certain edge cases (I don't remember exactly). I might look into it again at some point in the future. A per-window badge would greatly simplify this. I haven't created a bug, though.