[css-navigation-1] Add more detail to issue about base URL of urlpattern().

(This is part of importing the history from WICG/declarative-partial-updates.)

Author: dbaron

css-navigation-1/Overview.bs

@@ -245,17 +245,25 @@ using the steps of the <dfn>create a URL pattern for urlpattern()</dfn> algorith
 	the rule or declaration block containing the ''urlpattern()'' function.
 
 	<div class="issue">
-	Do we really want this to be the base URL?
-	For this particular use of ''urlpattern()'',
+	Do we want this to be the base URL all the time?
+	For use of ''urlpattern()'' in ''@route'',
 	it's likely more useful for the base URL
 	to be the document URL rather than the style sheet URL.
 	However, it would be very awkward for ''urlpattern()''
 	to be inconsistent with ''url()''.
+
+	Should we allow the base URL of ''urlpattern()''
+	to be defined by the consumer?
 	Should we introduce <code>document-urlpattern()</code>?
 	Should we do something similar to
 	[[css-images-3#ambiguous-urls]]
 	(see <w3c/csswg-drafts#383>)?
 
+	Also see other proposed uses of {{URLPattern}} in CSS
+	in <w3c/csswg-drafts#10975>,
+	for '':local-link''.
+	</div>
+
 1. Return the result of [=URL pattern/create|create a URL pattern=] given
 	<var>arg</var>, <var>baseURL</var>, and an empty [=map=].