[css-values-5] Specify how to handle a too-large random() range. w3c#11634

Author: tabatkins

css-values-5/Overview.bs

@@ -2123,6 +2123,11 @@ Argument Ranges</h4>
 	If C is infinite,
 	the result is A.
 
+	If A and B are finite,
+	but the distance between them (''B - A'')
+	is large enough to become infinite in the user agent,
+	the result is NaN.
+
 	(If C is zero or negative,
 	the result is A,
 	but that falls out of the standard definition.)