reverted:
--- b/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInJavascriptTestBase.php
+++ a/core/modules/outside_in/tests/src/FunctionalJavascript/OutsideInJavascriptTestBase.php
@@ -10,19 +10,6 @@
 abstract class OutsideInJavascriptTestBase extends JavascriptTestBase {
 
   /**
-   * {@inheritdoc}
-   */
-  protected function drupalGet($path, array $options = array(), array $headers = array()) {
-    $return = parent::drupalGet($path, $options, $headers);
-
-    // After the page loaded we need to additionally wait until the settings
-    // tray Ajax activity is done.
-    $this->assertSession()->assertWaitOnAjaxRequest();
-
-    return $return;
-  }
-
-  /**
    * Enables a theme.
    *
    * @param string $theme