From bug 1114746 comment 2: The problem can be reproduces 100% of the time if for opening windows instead of tabs. Steps to reproduce: 1. create an add-on with 'let tabs = require('sdk/tabs')' (doesn't matter if you use let/var or const) 2. open around 10 new Firefox windows and then close them (except one) 3. windows not tabs 4. check in about:memory for --top(none)/detached 5. garbage collection or cycle collection or minimize memory usage does nothing tested with a clean profile on Firefox 34, and Nightly 6. disable the add-on 7. performing garbage collection now will free the memory used by those 10 windows

Chances are, the patch in bug 1224577 fixes this.

But note that the leaking addonw there didn't obviously require "sdk/tabs"...

And actually, the code bug 1224577 fixes postdates the comment cited in comment 0. So there might be a separate leak here.

Is there an example of an addon per comment 0 in this bug so we can retest once bug 1224577 is fixed?

I created a quick example and couldn't reproduce this with the fix from bug 1224577 so either this is a straight dupe or this specific case might have been fixed by bug 854982