Video elements flowed in a region do not show their contents. The controls however are visible.
Should be fixed once (or after) bug 120457 lands.
bug 120457 has been fixed.
a test is available at https://trac.webkit.org/browser/trunk/LayoutTests/compositing/regions/propagate-region-box-shadow-border-padding-for-video.html
Must recheck and close if appropriate.
Works in latest WebKit nightly (r158804). Closing as Fixed.