[css-anchor-position-1] Restore accidentally dropped text about CB ordering in one case. #11170

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -425,7 +425,11 @@ in anchor positioning.
 			* both elements' [=containing blocks=] are generated by elements,
 				and |positioned el|'s containing block
 				is an ancestor in the [=flat tree=]
-				to that of |possible anchor|'s [=containing block=].
+				to that of |possible anchor|'s [=containing block=],
+				and the last [=containing block=] in |possible anchor|'s [=containing block chain=]
+				before reaching |positioned el|'s [=containing block=]
+				is either not [=absolutely positioned=]
+				or precedes |positioned el| in the tree order.
 		* Both elements are [=in the same top layer=]
 			and have the same [=containing block=],
 			and are both [=absolutely positioned=],