[css-color-4] Restored parse-time clamping of HSL negative saturation to 0, which is current interop behavior from CSS Color 3. #9222

Author: svgeesus

css-color-4/Overview.bs

@@ -2125,12 +2125,16 @@ HSL Colors: ''hsl()'' and ''hsla()'' functions</h2>
 	and ''0%'' or ''0'' is a fully-unsaturated gray.
 	For lightness, ''50%'' or ''50'' represents the "normal" color,
 	while ''100%'' or ''100'' is white and ''0%''  or ''0'' is black.
-	<!--  unbounded hsl
-	If the saturation or lightness are less than ''0%''
-	or greater than ''100%'',
-	they are clamped to those values
+	
+	<!-- https://github.com/w3c/csswg-drafts/issues/9222 -->
+	If the saturation is less than ''0%''
+	it is clamped to ''0%''
 	at parsed-value time,
-	before being converted to an sRGB color. -->
+	before being converted to an sRGB color. 
+
+	<wpt>
+		t424-hsl-clip-outside-gamut-b.xht
+	</wpt>
 
 	The final argument specifies the alpha channel of the color.
 	It's interpreted identically to the fourth argument of the ''rgb()'' function.