[cssom-1] Export definition of "specified order"

Author: cdoublev

cssom-1/Overview.bs

@@ -2027,7 +2027,7 @@ following properties:
  <dd>Null.
 </dl>
 
-The <dfn id=concept-declarations-specified-order>specified order</dfn> for declarations is the same as specified, but with shorthand properties
+The <dfn export id=concept-declarations-specified-order>specified order</dfn> for declarations is the same as specified, but with shorthand properties
 expanded into their longhand properties, in canonical order. If a property is specified more than once (after shorthand expansion), only the
 one with greatest cascading order must be represented, at the same relative position as it was specified. [[!CSS3CASCADE]]