[css-values-5] Specify that style queries in if() introduce a dependency. #11500

Author: tabatkins

css-values-5/Overview.bs

@@ -1384,7 +1384,13 @@ Conditional Value Selection: the ''if()'' notation</h3>
 				otherwise, let the result be |condition|.
 
 			2. Evaluate |condition|.
-				If the result is false,
+
+				If a <<style-query>> in |condition| tests the value of a property,
+				and a &bs<<;"property", referenced-property-name&bs>>; [=substitution context=]
+				would be a [=cyclic substitution context=],
+				that query evaluates to false.
+
+				If the result of |condition| is false,
 				[=iteration/continue=].
 
 			3. [=Substitute arbitrary substitution functions=] in the second <<declaration-value>> of |branch|,