[css-align-3] Block containers default to safe alignment w3c#8992

Author: fantasai

css-align-3/Overview.bs

@@ -877,7 +877,8 @@ Overflow Alignment: the ''safe'' and ''unsafe'' keywords and scroll safety limit
 			(though we hope so, and believe it to be likely),
 			so UAs should pass any feedback on this point to the WG.
 			UAs that have not implemented the “smart” default behavior
-			must behave as ''unsafe''.
+			must behave as ''safe'' for 'align-content' on [=block containers=]
+			and ''unsafe'' otherwise.
 	</dl>
 
 
@@ -954,6 +955,9 @@ The 'justify-content' and 'align-content' Properties</h3>
 				The <a>block axis</a>.
 				If a <<content-distribution>> is specified
 				its <a>fallback alignment</a> is used instead.
+				If no <<overflow-position>> is specified,
+				and the [=block container=] is not a [=scroll container=],
+				then alignment is ''align-content/safe''.
 		<tr>
 			<th>'justify-content' Axis
 			<td>
@@ -2457,6 +2461,8 @@ Changes</h2>
 		<li>Only apply the special margin-edge baseline rule for [=scroll container=] [=block containers=]
 			when 'baseline-source' is its [=initial value=].
 			(<a href="https://github.com/w3c/csswg-drafts/issues/8214">Issue 8214</a>)
+		<li>Made [=block containers=] default to ''safe'' alignment.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/8992">Issue 8992</a>)
 	</ul>
 
 	Changes since the <a href="https://www.w3.org/TR/2021/WD-css-align-3-20211224/">24 December 2021 Working Draft</a> include: