[css-sizing-3] Define intrinsic sizes of fit-content(). w3c#3731

Author: fantasai

css-sizing-3/Overview.bs

@@ -458,6 +458,11 @@ Sizing Values: the <<length-percentage>>, ''width/auto'' | ''max-width/none'', '
 			i.e.
 			<code>min(''width/max-content'', max(''width/min-content'', <<length-percentage>>))</code>;
 			otherwise behaves as the property’s <a>initial value</a>.
+			For <a>intrinsic size contributions</a>,
+			''fit-content(<<length>>)'' behaves as the resulting length;
+			''width/fit-content()'' containing a <<percentage>> behaves
+			as ''width/min-content'' for <a>min-content contributions</a>,
+			and as ''width/max-content'' for <a>max-content contributions</a>.
 
 			Negative values are invalid.
 	</dl>