drupal_get_form() to initiate an existing or new class name

Summary

• Drupal 7, forms were built by a procedural function, and validation and submission were named functions.
• In Drupal 8, there is now an interface called FormInterface with four methods:
  getFormID(), buildForm(), validateForm(), submitForm()
• Refer FormInterface Change Request at: https://drupal.org/node/1932058
• This change request cleans up drupal_get_form() to initiate an existing or new class name

Before

drupal_get_form(new SearchBlockForm());
drupal_get_form(ConfirmDeleteMultiple::create(\Drupal::getContainer()));

drupal_get_form was used as - return drupal_get_form(new SearchBlockForm(), $this->request);

After

drupal_get_form('Drupal\comment\Form\ConfirmDeleteMultiple');
drupal_get_form('Drupal\search\Form\SearchBlockForm');

drupal_get_form now used as - return drupal_get_form('Drupal\search\Form\SearchBlockForm');