[css-grid][editorial] Add mention of aspect-ratio to the note listing possible causes for running steps 3/4 of Grid Layout. w3c#6356

Author: tabatkins

css-grid-1/Overview.bs

@@ -3853,7 +3853,9 @@ Grid Sizing Algorithm</h3>
 				depends on the <a>block size</a> of its <a>grid area</a>.
 				Examples include wrapped column <a>flex containers</a> (''flex-flow: column wrap''),
 				<a>orthogonal flows</a> ('writing-mode'),
-				and <a spec=css-multicol>multi-column containers</a>.
+				<a spec=css-multicol>multi-column containers</a>,
+				and items with an aspect-ratio (or with a child with an aspect ratio)
+				whose size depends on the size of the row.
 			</div>
 
 		<li>

css-grid-2/Overview.bs

@@ -4412,7 +4412,9 @@ Grid Sizing Algorithm</h3>
 				depends on the <a>block size</a> of its <a>grid area</a>.
 				Examples include wrapped column <a>flex containers</a> (''flex-flow: column wrap''),
 				<a>orthogonal flows</a> ('writing-mode'),
-				and <a spec=css-multicol>multi-column containers</a>.
+				<a spec=css-multicol>multi-column containers</a>,
+				and items with an aspect-ratio (or with a child with an aspect ratio)
+				whose size depends on the size of the row.
 			</div>
 
 		<li>