Issue #3073808 - Fix deprecated methods

Closes #3073808

conditional_styles.module

@@ -5,16 +5,19 @@
  * Adds conditional CSS from the .info file.
  */
 
-use \Drupal\Component\Utility\Unicode;
+use Drupal\Core\Asset\AttachedAssetsInterface;
 
 /**
  * Implements hook_css_alter().
  */
-function conditional_styles_css_alter(&$css, \Drupal\Core\Asset\AttachedAssetsInterface $assets) {
+function conditional_styles_css_alter(&$css, AttachedAssetsInterface $assets) {
+  /** @var \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler */
   $theme_handler = \Drupal::service('theme_handler');
   $current_theme = $theme_handler->getDefault();
-  $path = drupal_get_path('theme', $current_theme);
+
+  $path = \Drupal::service('extension.list.theme')->getPath($current_theme);
   $info = $theme_handler->getTheme($current_theme)->info;
+
   if (!empty($info['conditional-stylesheets'])) {
     foreach ($info['conditional-stylesheets'] as $version => $media) {
       foreach ($media as $key => $file_path) {
@@ -29,7 +32,7 @@ function conditional_styles_css_alter(&$css, \Drupal\Core\Asset\AttachedAssetsIn
           'every_page' => TRUE,
           'browsers' => [
             'IE'  => $version,
-            '!IE' => (Unicode::strpos($version, '!IE') !== FALSE),
+            '!IE' => (mb_strpos($version, '!IE') !== FALSE),
           ],
         ];
       }