[css-flexbox] Export 'flex line'.

--HG--
extra : rebase_source : 425e142ebbff4b2bb4b1d4c3f8211cf3126ba308

Author: tabatkins

css-flexbox/Overview.bs

@@ -1124,7 +1124,7 @@ Flex Lines</h2>
 
 	<p>
 		<a>Flex items</a> in a <a>flex container</a> are laid out and aligned
-		within <dfn title="flex line">flex lines</dfn>,
+		within <dfn export title="flex line">flex lines</dfn>,
 		hypothetical containers used for grouping and alignment by the layout algorithm.
 		A flex container can be either <i>single-line</i> or <i>multi-line</i>,
 		depending on the 'flex-wrap' property: