Move frontpage handling to the PathSubscriber.

core/lib/Drupal/Core/EventSubscriber/PathSubscriber.php

@@ -39,6 +39,11 @@ public function onKernelRequestPathResolve(GetResponseEvent $event) {
     }
     $system_path = drupal_get_normal_path($path);
 
+    // Do our fancy frontpage logic.
+    if (empty($system_path)) {
+      $system_path = variable_get('site_frontpage', 'user');
+    }
+
     $request->attributes->set('system_path', $system_path);
 
     // @todo Remove this line once code has been refactored to use the request

core/lib/Drupal/Core/UrlMatcher.php

@@ -94,11 +94,6 @@ public function match($pathinfo) {
       $dpathinfo = ltrim($pathinfo, '/');
     }
 
-    // Do our fancy frontpage logic.
-    if (empty($dpathinfo)) {
-      $dpathinfo = variable_get('site_frontpage', 'user');
-    }
-
     if ($router_item = $this->matchDrupalItem($dpathinfo)) {
       $ret = $this->convertDrupalItem($router_item);
       // Stash the router item in the attributes while we're transitioning.