Make sure the first party isolation patches in ESR52 behave as they should
We plan to abandon our first party isolation patches and use those in Firefox 52 instead. While the behavior should not change I think we should make sure that this is and will (for the future) be indeed the case. I am not so sure about the best way to achieve this, though. Is it just a matter of running our tbb-tests as soon as we switched to ESR52? Or can and should we do more?