[css-values-4] Switch ratio interpolation to the other possibility - divided value interpolation. Closes w3c#4953.

Author: tabatkins

css-values-4/Overview.bs

@@ -1284,27 +1284,21 @@ Ratios: the <<ratio>> type</h3>
 Combination of <<ratio>></h4>
 
 	The interpolation of a <<ratio>> is defined
-	by interpolating the first values (the numerator)
-	of each ratio as a <<number>>,
-	and the second values (the denominator)
-	or each ratio as a <<number>>.
+	by converting each <<ratio>> to an equivalent form
+	with a ''1'' as its second value
+	(so a ratio of ''3 / 2'' would become ''1.5 / 1''),
+	then interpolating the numbers directly.
 
 	<div class='example'>
 		For example,
 		halfway through a linear interpolation from ''5 / 1'' to ''3 / 2'',
-		the result is the ratio ''4 / 1.5''.
-
-		Note that this means the results are scale-dependent;
-		interpolating from ''5 / 1'' to ''300 / 200'',
-		which have identical-looking endpoints,
-		gives the value ''152.5 / 100.5'' at the halfway point,
-		which is very close to the 3:2 ratio of the endpoint.
-		In general, if one ratio is written with much larger numbers than the other,
-		the interpolation result spends most of its time
-		very close to the large-number ratio.
-	</div>
+		the result is the ratio ''3.25 / 1'',
+		because 3.25 is halfway between 5 and 1.5.
 
-	Issue: This is being discussed in <a href="https://github.com/w3c/csswg-drafts/issues/4953">Issue 4953</a>.
+		Note that this means the results are <em>not</em> scale-dependent;
+		interpolating from ''5 / 1'' to ''300 / 200''
+		gives the same results as the preceding example.
+	</div>
 
 	Addition of <<ratio>>s is not possible.