[css-values-4] round(A, inf) needs to be depend on the rounding strategy. Fixes w3c#4725.

Author: tabatkins

css-values-4/Overview.bs

@@ -2761,19 +2761,26 @@ Argument Ranges</h4>
 	In ''round(A, B)'',
 	if B is 0,
 	the result is NaN.
-	If both A and B are infinite,
-	the result is NaN.
 
-	If A is +∞ and B is finite,
-	the result is +∞.
-	If A is −∞ and B is finite,
-	the result is −∞.
-
-	If A is finite
-	and B is infinite,
-	the result is 0⁺
-	if A is 0⁺ or positive finite,
-	and 0⁻ if A is 0⁻ or negative finite.
+	If A is infinite,
+	the result is the same infinity.
+
+	If A is finite but B is infinite,
+	the result depends on the <<rounding-strategy>>
+	and the sign of A:
+
+	: ''nearest''
+	: ''to-zero''
+	:: If A is positive or 0⁺, return 0⁺.
+		Otherwise, return 0⁻.
+	: ''up''
+	:: If A is positive (not zero), return +∞.
+		If A is 0⁺, return 0⁺.
+		Otherwise, return 0⁻.
+	: ''down''
+	:: If A is negative (not zero), return −∞.
+		If A is 0⁻, return 0⁻.
+		Otherwise, return 0⁺.
 
 	In ''mod(A, B)'' or ''rem(A, B)'',
 	if B is 0,