Meta: export a user agent's top-level traversable set

Needed by the Notifications API: whatwg/notifications#213.

Author: annevk

source

@@ -96988,9 +96988,9 @@ interface <dfn interface>NotRestoredReasons</dfn> {
   are <span data-x="top-level traversable">top-level traversables</span>. Future proposals envision
   introducing non-top-level traversables.</p>
 
-  <p>A user agent holds a <dfn>top-level traversable set</dfn> (a <span>set</span> of <span
-  data-x="top-level traversable">top-level traversables</span>). These are typically presented to
-  the user in the form of browser windows or browser tabs.</p>
+  <p>A user agent holds a <dfn export for="user agent">top-level traversable set</dfn> (a
+  <span>set</span> of <span data-x="top-level traversable">top-level traversables</span>). These are
+  typically presented to the user in the form of browser windows or browser tabs.</p>
 
   <p>To get the <dfn export for="navigable" data-x="nav-top">top-level traversable</dfn> of a
   <span>navigable</span> <var>inputNavigable</var>:</p>