[css-display-3] Resolve min-width: auto to zero on elements without a box. #3557

Author: fantasai

css-sizing-3/Overview.bs

@@ -392,6 +392,8 @@ Sizing Values: the <<length-percentage>>, ''width/auto'' | ''max-width/none'', '
 			block and inline boxes,
 			inline blocks,
 			and all the table layout boxes.
+			It also resolves to zero
+			when no box is generated.
 
 		<dt><dfn for="max-width, max-height">none</dfn>
 		<dd>