Created attachment 203456 [details]
In case of simple DOM nesting, applying a transform on an element and the inverse transform on the parent should render as if no transforms were applied.
However, if a 3D transform is applied to content flowed in a region and the inverse transform is applied to the region, the result still has some residual transformation applied. This bug is most likely related to bug 114293 where the perspective is not obeyed.
Created attachment 203530 [details]
Still repros on today's nightly (r151543)