[css-grid] If an abspos's parent *and* positioning root is the same grid container, use the grid-placement properties to find its static position, too.

Author: tabatkins

css-grid/Overview.bs

@@ -2536,7 +2536,7 @@ Grid Item Placement Algorithm</h3>
 	if there is no room in the <a>explicit grid</a> to place an auto-positioned <a>grid item</a>.
 
 	Every <a>grid cell</a>
-	(in both the <a lt="explicit grid">explicit</a> and <a>implicit grids</a>)
+	(in both the <a>explicit</a> and <a>implicit grids</a>)
 	can be <dfn>occupied</dfn> or <dfn>unoccupied</dfn>.
 	A cell is <a>occupied</a>
 	if it's covered by a <a>named grid area</a>,
@@ -2782,6 +2782,8 @@ With a Grid Container as Parent</h3>
 	is determined as if it were the sole grid item
 	in a <a>grid area</a>
 	whose edges coincide with the padding edges of the <a>grid container</a>.
+	However, if the <a>grid container</a> parent is also the generator of the absolutely positioned element's <a>containing block</a>,
+	instead use the <a>grid area</a> determined in [[#abspos-items]].
 
 	Note: Note that this position is affected by the values of 'justify-self' and 'align-self' on the child,
 	and that, as in most other layout models,