[css-exclusions] Shrink to fit around content of exclusion area

I was reviewing this specification this evening and can't seem to find anything that states that the result of the exclusion area's size must be that of its contents if the exclusion element(s) have auto sizing. Testing IE/Edge the size of the exclusion area, when left in auto sizing results in the measurement of the content [1]


[1] http://codepen.io/gregwhitworth/pen/mPxgWW

I may have missed it, but it seems like stating this explicitly in the definitions for an exclusion area and in section 3.5.4 Step-2A: https://drafts.csswg.org/css-exclusions/#step-2-A would be helpful.

Thanks,
Greg