[css-position-3] Define automatic sizing of non-replaced abspos boxes with an aspect ratio. w3c#5151

Author: fantasai

css-position-3/Overview.bs

@@ -885,6 +885,16 @@ Automatic Sizes of Absolutely-Positioned Boxes</h3>
 		or if it is ''align-self/normal'' and the box is [=replaced=],
 		its [=automatic size=] is its [=fit-content size=].
 
+	However, if the box has an aspect-ratio,
+	then an [=automatic size=] in the [=ratio-dependent=] axis
+	is instead resolved as a [=max-content size=].
+	When both axes have an [=automatic size=],
+	if only one axis has an ''inset/auto'' inset
+	then that axis is the [=ratio-dependent=] axis,
+	else the [=inline axis=] is the [=ratio-dependent=] axis.
+	An [=automatic size=] in the [=ratio-determining=] axis
+	is determined as above.
+
 	The [=automatic minimum size=] of an absolutely-positioned box is always zero.
 
 <h3 id="abspos-margins">
@@ -1624,7 +1634,15 @@ Acknowledgments</h2>
 <h2 class="no-num" id="changes">Changes</h2>
 
 	The following significant changes were made since the
-	<a href="https://www.w3.org/TR/2016/WD-css-position-3-20160517/">17 May 2016 Working Draft</a>
+	<a href="https://www.w3.org/TR/2020/WD-css-position-3-20200519/">19 May 2020 Working Draft</a>:
+
+	<ul>
+		<li>Defined automatic sizing of non-replaced absolutely-positioned boxes with an aspect ratio.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/5151">Issue 5151</a>)
+	</ul>
+
+	The following significant changes were made since the
+	<a href="https://www.w3.org/TR/2016/WD-css-position-3-20160517/">17 May 2016 Working Draft</a>:
 
 	<ul>
 		<li>Rewrote the whole spec for editorial clarity, technical precision, and compatibility with [[CSS-ALIGN-3]], [[CSS-WRITING-MODES-3]], [[CSS-BREAK-3]], and [[CSS-DISPLAY-3]].