Beginnings of rendering image normally in the branding block.

Closes #3345259

core/modules/system/src/Plugin/Block/SystemBrandingBlock.php

@@ -151,12 +151,22 @@ public function build() {
     $build = [];
     $site_config = $this->configFactory->get('system.site');
 
+    $logo_uri = theme_get_setting('logo.url');
     $build['site_logo'] = [
       '#theme' => 'image',
-      '#uri' => theme_get_setting('logo.url'),
+      '#uri' => $logo_uri,
       '#alt' => $this->t('Home'),
+      '#attributes' => ['loading' => 'eager', 'fetchpriority' => 'high'],
       '#access' => $this->configuration['use_site_logo'],
     ];
+    $image = \Drupal::service('image.factory')->get($logo_uri);
+    if ($image->isValid()) {
+      $build['site_logo']['width'] = $image->getWidth();
+      $build['site_logo']['height'] = $image->getHeight();
+    }
+    else {
+      dump('boo');
+    }
 
     $build['site_name'] = [
       '#markup' => $site_config->get('name'),