Currently whenever we have a masonry grid we perform two iterations of item placement. The first item placement is done as if we had grid-template-rows (or columns) set to none when the masonry axis is rows (or columns). This is done to figure out which items are placed at the first implicit line for masonry layout. The second iteration is the item placement according to the masonry layout algorithm. We should be able to short circuit the initial placement once we have figured out all of the items that are placed at the first initial line.