[css-flexbox-1] Clarify that flex base size calculations involving an aspect ratio take the *used* cross size as input. w3c#3736

Author: fantasai

css-flexbox-1/Overview.bs

@@ -2536,7 +2536,8 @@ Line Length Determination</h3>
 						<li>a used <a>flex basis</a> of ''content'', and
 						<li>a <a>definite</a> <a>cross size</a>,
 					</ul>
-					then the <a>flex base size</a> is calculated from its inner <a>cross size</a>
+					then the <a>flex base size</a> is calculated from
+					its <a lt="used value">used</a> <a lt="inner size">inner</a> <a>cross size</a>
 					and the <a>flex item</a>’s intrinsic aspect ratio.
 
 				<li>
@@ -3677,6 +3678,21 @@ Boris Zbarsky.
 
 	This section documents the changes since previous publications.
 
+<h3 id="changes-20181119">
+Changes since the <a href="https://www.w3.org/TR/2018/CR-css-flexbox-1-20181119/">19 November 2018 CR</a></h3>
+
+	<ul>
+		<li id="change-2018-used-cross-size">
+			Clarified that the [=flex base size=] calculations
+			rely on the <em>used</em> [=cross size=].
+			(<a href="https://github.com/w3c/csswg-drafts/issues/3736">Issue 3736</a>)
+			<blockquote>
+				<p>&hellip; then the flex base size is calculated from
+				its <ins>used</ins> inner cross size
+				and the flex item’s intrinsic aspect ratio.
+			</blockquote>
+	</ul>
+
 <h3 id="changes-20171016">
 Changes since the 16 October 2017 CR</h3>