Replace confusing paragraph with issue.

Author: tabatkins

css3-flexbox/Overview.src.html

@@ -1128,9 +1128,10 @@ <h2 id='layout-algorithm'>
 					Repeat until all flexbox items have been collected into flexbox lines.
 			</ul>
 
-		<li>Find the actual main size of the flexbox.  If the flexbox's main size doesn't rely on its contents, its actual main size is calculated per the appropriate rules.  Otherwise, its main size is the length of its longest line, calculated by summing the main sizes of the margin boxes of each flexbox item in the line, constrained by the flexbox's min and max main size constraints. 
-		If any margins are set to ''auto'', consider them to be set to zero until 
-		resolved in a separate step.</li>
+		<li>
+			<p class='issue'>
+				Are flexboxes fill-available or fit-content by default?  
+				Or are they really shrink-wrap, such that we need to adjust the main size here, now that we know the length of the longest line?
 
 		<li>For each flexbox line, 
 		<ol>