Update src/js/tech/middleware.js per feedback

Co-authored-by: Gary Katsevman <git@gkatsev.com>

src/js/tech/middleware.js

@@ -92,7 +92,7 @@ export function setSource(player, src, next) {
  * @return {Tech~SourceObject}
  *         A source object.
  */
-export function currentSource(src, middleware) {
+export function currentSource(middleware, src) {
   return middleware.reduceRight(middlewareIterator('currentSource'), src);
 }