[css-font-loading-3] Use and/or export a few definitions that Bikeshed was complaining about.

Author: tabatkins

css-font-loading-3/Overview.bs

@@ -489,7 +489,7 @@ The <code>FontFaceSet</code> Interface</h2>
 			must iterate its {{initialFaces}} argument
 			and add each value to its [=FontFaceSet/set entries=].
 
-		: <dfn dfn>iteration order</dfn>
+		: <dfn dfn export>iteration order</dfn>
 		:: When iterated over,
 			all <a>CSS-connected</a> {{FontFace}} objects must come first,
 			in document order of their connected ''@font-face'' rules,
@@ -714,7 +714,7 @@ Events</h3>
 			and <var>font style</var> be the other font style attributes parsed from <var>font</var>.
 
 		<li>
-			Let <var>available font faces</var> be the font faces within <var>source</var>.
+			Let <var>available font faces</var> be the [=available font faces=] within <var>source</var>.
 			If the <var>allow system fonts</var> flag is specified,
 			add all system fonts to <var>available font faces</var>.
 
@@ -1011,7 +1011,7 @@ The <code>FontFaceSource</code> mixin</h2>
 	Operations referring to “the font source” must be interpreted as referring to the <a>font source</a> of the relevant context in which the operation is taking place.
 
 	For any font-related operation that takes place within one of these contexts,
-	the {{FontFace}} objects within the <a>font source</a> are its <dfn>available font faces</dfn>.
+	the {{FontFace}} objects within the <a>font source</a> are its <dfn export>available font faces</dfn>.
 
 <h3 id="fontfacesource-workers">
 Worker FontFaceSources</h3>