PopupWidget: Toggle clipping -after- updating dimensions

ClippableElement#toggleClipping no longer clips asynchronously (I60742642), so we need to call it
after we've set the dimensions.

Bug: 70423
Change-Id: I1a6fda4091bc9b35eb28cf4832095d0bb1565f05
Merge "PopupWidget: Toggle clipping -after- updating dimensions"