Issue #2797721 by jp.stacey: Custom form handler's submitForm not called when...

Issue #2797721 by jp.stacey: Custom form handler's submitForm not called when using example in documentation

core/core.api.php

@@ -1692,7 +1692,11 @@
  *     // Create a $form API array.
  *     $form['phone_number'] = array(
  *       '#type' => 'tel',
- *       '#title' => $this->t('Your phone number')
+ *       '#title' => $this->t('Your phone number'),
+ *     );
+ *     $form['save'] = array(
+ *       '#type' => 'submit',
+ *       '#value' => $this->t('Save'),
  *     );
  *     return $form;
  *   }