diff --git a/core/modules/outside_in/outside_in.libraries.yml b/core/modules/outside_in/outside_in.libraries.yml
index 574d7ed656..5c388b82f1 100644
--- a/core/modules/outside_in/outside_in.libraries.yml
+++ b/core/modules/outside_in/outside_in.libraries.yml
@@ -20,8 +20,6 @@ drupal.outside_in:
     - core/drupal
     - core/jquery.once
     - core/drupal.ajax
-    - core/drupalSettings
-    - core/jquery.form
 drupal.off_canvas:
   version: VERSION
   js:
diff --git a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
index f473d18ee6..8e74754fdb 100644
--- a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
+++ b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
@@ -8,6 +8,7 @@
 use Drupal\Core\Form\DialogFormTrait;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginWithFormsInterface;
+use Drupal\outside_in\OffCanvasFormDialogTrait;
 
 /**
  * Provides form for block instance forms when used in the off-canvas dialog.
@@ -19,7 +20,7 @@
  */
 class BlockEntityOffCanvasForm extends BlockForm {
 
-  use DialogFormTrait;
+  use OffCanvasFormDialogTrait;
 
   /**
    * Provides a title callback to get the block's admin label.
diff --git a/core/lib/Drupal/Core/Form/DialogFormTrait.php b/core/modules/outside_in/src/OffCanvasFormDialogTrait.php
similarity index 80%
rename from core/lib/Drupal/Core/Form/DialogFormTrait.php
rename to core/modules/outside_in/src/OffCanvasFormDialogTrait.php
index dead12f3fd..2f0da18b01 100644
--- a/core/lib/Drupal/Core/Form/DialogFormTrait.php
+++ b/core/modules/outside_in/src/OffCanvasFormDialogTrait.php
@@ -1,37 +1,51 @@
 <?php
 
-namespace Drupal\Core\Form;
+namespace Drupal\outside_in;
 
-use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\CloseDialogCommand;
 use Drupal\Core\Ajax\RedirectCommand;
 use Drupal\Core\Ajax\ReplaceCommand;
 use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
-use Drupal\Core\Ajax\AjaxResponse;
-use Drupal\Core\Ajax\CloseDialogCommand;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Url;
 
 /**
- * Provides utilities for forms that want to be rendered in dialogs.
+ * Helper trait for forms that are used in the off-canvas dialog.
+ *
+ * Classes that use this trait should implement \Drupal\Core\Form\FormInterface.
+ *
+ * @internal
+ *   This trait will likely be replace with a common API for handling form
+ *   submissions in dialogs.
+ *   @todo Remove in https://www.drupal.org/node/2896535.
  */
-trait DialogFormTrait {
+trait OffCanvasFormDialogTrait {
+
+  /**
+   * Determines if the current request is for an AJAX modal dialog.
+   *
+   * @return bool
+   *   TRUE is the current request if for an AJAX modal dialog.
+   */
+  protected function isOffCanvasDialog() {
+    $wrapper_format = $this->getRequest()
+      ->get(MainContentViewSubscriber::WRAPPER_FORMAT);
+    return $wrapper_format === 'drupal_dialog.off_canvas';
+  }
 
   /**
-   * Adds dialog support to a form.
+   * Adds modal dialog support to a form.
    *
    * @param array $form
    *   An associative array containing the structure of the form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
-   * @param bool $create_cancel
-   *   If TRUE the create submit button will be created.
-   * @param string $dialog_selector
-   *   The CSS selector for the associated dialog.
    */
-  protected function buildFormDialog(array &$form, FormStateInterface $form_state, $create_cancel = FALSE, $dialog_selector = '#drupal-modal') {
-    if (!$this->isDialog()) {
+  protected function buildFormDialog(array &$form, FormStateInterface $form_state) {
+    if (!$this->isOffCanvasDialog()) {
       return;
     }
-    $form_state->set('dialog_selector', $dialog_selector);
 
     $ajax_callback_added = FALSE;
 
@@ -45,62 +59,36 @@ protected function buildFormDialog(array &$form, FormStateInterface $form_state,
       $ajax_callback_added = TRUE;
     }
 
-    if ($create_cancel) {
-      $form['actions']['cancel'] = [
-        '#type' => 'submit',
-        '#value' => $this->t('Cancel'),
-        '#weight' => 100,
-      ];
-    }
     if (!empty($form['actions']['cancel'])) {
       // Replace 'Cancel' link button with a close dialog button.
       $form['actions']['cancel'] = [
+        '#type' => 'submit',
+        '#value' => $this->t('Cancel'),
         '#submit' => ['::noSubmit'],
         '#limit_validation_errors' => [],
+        '#weight' => 100,
         '#ajax' => [
           'callback' => '::closeDialog',
           'event' => 'click',
         ],
-      ] + $form['actions']['cancel'];
+      ];
       $ajax_callback_added = TRUE;
     }
 
     if ($ajax_callback_added) {
       $form['#attached']['library'][] = 'core/drupal.dialog.ajax';
-      $form['#attributes']['id'] = 'dialog-form';
+      $form['#attributes']['id'] = 'off-canvas-form';
     }
   }
 
   /**
-   * Empty submit #ajax submit callback.
-   *
-   * This allows modal dialog to using ::submitCallback to validate and submit
-   * the form via one ajax required.
-   *
-   * @param array $form
-   *   An associative array containing the structure of the form.
-   * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The current state of the form.
-   */
-  public function noSubmit(array &$form, FormStateInterface $form_state) {
-  }
-
-
-
-  /**
-   * Determines if the current request is for an AJAX dialog.
-   *
-   * @return bool
-   *   TRUE is the current request if for an AJAX dialog.
+   * @return mixed
    */
-  protected function isDialog() {
-    return in_array($this->getRequestWrapperFormat(), [
-      'drupal_dialog',
-      'drupal_modal',
-      'drupal_dialog.off_canvas',
-    ]);
+  protected function getRequestWrapperFormat() {
+    $wrapper_format = $this->getRequest()
+      ->get(MainContentViewSubscriber::WRAPPER_FORMAT);
+    return $wrapper_format;
   }
-
   /**
    *
    */
@@ -139,7 +127,7 @@ public function submitFormDialog(array &$form, FormStateInterface $form_state) {
         '#type' => 'status_messages',
         '#weight' => -1000,
       ];
-      $command = new ReplaceCommand('#dialog-form', $form);
+      $command = new ReplaceCommand('#off-canvas-form', $form);
     }
     else {
       if ($redirect_url = $this->getRedirectUrl()) {
@@ -164,17 +152,21 @@ public function submitFormDialog(array &$form, FormStateInterface $form_state) {
    *   An AJAX response that display validation error messages.
    */
   public function closeDialog(array &$form, FormStateInterface $form_state) {
-    $selector = $form_state->get('dialog_selector');
-    return (new AjaxResponse())->addCommand(new CloseDialogCommand($selector));
+    return (new AjaxResponse())->addCommand(new CloseDialogCommand('#drupal-off-canvas'));
   }
 
   /**
-   * @return mixed
+   * Empty submit #ajax submit callback.
+   *
+   * This allows modal dialog to using ::submitCallback to validate and submit
+   * the form via one ajax required.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
    */
-  protected function getRequestWrapperFormat() {
-    $wrapper_format = $this->getRequest()
-      ->get(MainContentViewSubscriber::WRAPPER_FORMAT);
-    return $wrapper_format;
+  public function noSubmit(array &$form, FormStateInterface $form_state) {
   }
 
   /**
@@ -198,8 +190,7 @@ protected function getRedirectUrl() {
    */
   protected function getDestinationUrl() {
     if ($destination = $this->getRedirectDestinationPath()) {
-      $options = UrlHelper::parse($destination);
-      return Url::fromUserInput('/' . ltrim($options['path'], '/'), $options);
+      return Url::fromUserInput('/' . $destination);
     }
   }
 
diff --git a/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php b/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
index 3812e40ca9..eaddd816f0 100644
--- a/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
+++ b/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
@@ -2,16 +2,16 @@
 
 namespace Drupal\off_canvas_test\Form;
 
-use Drupal\Core\Form\DialogFormTrait;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\outside_in\OffCanvasFormDialogTrait;
 
 /**
  * Just a test form.
  */
 class TestForm extends FormBase {
 
-  use DialogFormTrait;
+  use OffCanvasFormDialogTrait;
 
   /**
    * {@inheritdoc}