[css-flexbox] Editorial rewrite of the 2nd definiteness special-case to make it much clearer.

Author: tabatkins

css-flexbox/Overview.bs

@@ -2696,14 +2696,10 @@ Definite and Indefinite Sizes</h3>
 			and is considered <a>definite</a>.
 
 		<li>
-			If a percentage is going to be resolved against a <a>flex item’s</a> <a>main size</a>,
-			and the <a>flex item</a> has a <a>definite</a> <a>flex basis</a>,
+			If a <a>flex item</a> has a <a>definite</a> <a>flex basis</a>
 			and the <a>flex container</a> has a <a>definite</a> <a>main size</a>,
-			the <a>flex item’s</a> <a>main size</a> must be treated as <a>definite</a>
-			for the purpose of resolving the percentage,
-			and the percentage must resolve against the <strong>flexed</strong> <a>main size</a> of the <a>flex item</a>
-			(that is, after the layout algorithm below has been completed for the <a>flex item’s</a> <a>flex container</a>,
-				and the <a>flex item</a> has acquired its final size).
+			its post-flexing main size is treated as <a>definite</a>
+			(even though it might technically rely on the sizes of <a>indefinite</a> siblings to resolve its flexed main size).
 
 		<li>
 			Once the cross size of a flex line has been determined,
@@ -2748,6 +2744,7 @@ Flex Container Intrinsic Main Sizes</h4>
 			If that result is not zero, divide it by (if the result was positive) its <a>flex grow factor</a> floored at 1,
 			or (if the result was negative) by its <a>scaled flex shrink factor</a>, having floored the <a>flex shrink factor</a> at 1.
 			This is the item's <var>max-content flex fraction</var>.
+
 		<li>
 			Place all <a>flex items</a> into lines of infinite length.