The case for computing auto-height of block elements which have block-
level children was erroneously skipping some children:
1. If the block element itself is absolute or floating, all children
were skipped due to a likely typo ("box" vs. "child_box" inside the
for-each loop).
2. Floating children should only be skipped if the block element's
'overflow' property computes to 'visible', per section 10.6.3 of the
CSS height property spec. If the property computes to another value,
section 10.6.7 only indicates that absolutely positioned children
should be skipped.