diff --git a/core/misc/dialog/offcanvas.css b/core/misc/dialog/offcanvas.css
index fb671db..0e46c6a 100644
--- a/core/misc/dialog/offcanvas.css
+++ b/core/misc/dialog/offcanvas.css
@@ -1,23 +1,39 @@
 /**
  * @file
  * CSS for Offcanvas tray.
- *
- * @todo Move CSS into core dialog library https://www.drupal.org/node/2784443.
  */
 /* Position the dialog-offcanvas tray container outside the right of the viewport. */
 .ui-dialog-offcanvas {
-    box-sizing: border-box;
-    height: 100%;
-    overflow: visible;
+  box-sizing: border-box;
+  height: 100%;
+  overflow: visible;
 }
 
 /* Wrap the form that's inside the dialog-offcanvas tray. */
 .ui-dialog-offcanvas .ui-dialog-content {
-    padding: 0 20px;
-    /* Prevent horizontal scrollbar. */
-    overflow-x: hidden;
-    overflow-y: auto;
+  padding: 0 20px;
+  /* Prevent horizontal scrollbar. */
+  overflow-x: hidden;
+  overflow-y: auto;
 }
+
 [dir="rtl"] .ui-dialog-offcanvas .ui-dialog-content {
-    text-align: right;
+  text-align: right;
+}
+
+/*
+ * Force the tray to be 100% width at the same breakpoint the dialog system uses
+ * to expand dialog widths.
+ */
+@media all and (max-width: 48em) {
+  /* 768px */
+  .ui-dialog.ui-dialog-offcanvas {
+    width: 100% !important;
+  }
+
+  /* When tray is at 100% width stop the body from scrolling */
+  .js-tray-open {
+    height: 100%;
+    overflow-y: hidden;
+  }
 }
diff --git a/core/misc/dialog/offcanvas.js b/core/misc/dialog/offcanvas.js
index 8cda69d..7493e0a 100644
--- a/core/misc/dialog/offcanvas.js
+++ b/core/misc/dialog/offcanvas.js
@@ -1,10 +1,6 @@
 /**
  * @file
  * Drupal's off-canvas library.
- *
- * @todo This functionality should extracted into a new core library or a part
- *  of the current drupal.dialog.ajax library.
- *  https://www.drupal.org/node/2784443
  */
 
 (function ($, Drupal, debounce, displace) {
@@ -12,7 +8,7 @@
   'use strict';
 
   // The minimum width to use body displace needs to match the width at which
-  // the tray will be %100 width. @see outside_in.module.css
+  // the tray will be %100 width. @see offcanvas.css
   var minDisplaceWidth = 768;
 
   /**
diff --git a/core/misc/dialog/offcanvas.motion.css b/core/misc/dialog/offcanvas.motion.css
index 1c06994..7228a29 100644
--- a/core/misc/dialog/offcanvas.motion.css
+++ b/core/misc/dialog/offcanvas.motion.css
@@ -5,24 +5,23 @@
  * Motion effects are in a separate file so that they can be easily turned off
  * to improve performance if desired.
  *
- * @todo Move motion effects file into a core Off-Canvas library and add a
- *   configuration option for browser rendering performance to disable this
- *   file: https://www.drupal.org/node/2784443.
+ * @todo Add a configuration option for browser rendering performance to disable
+ *   this file: https://www.drupal.org/node/2784443.
  */
 
 /* Transition the dialog-offcanvas tray container, with 2s delay to match main canvas speed. */
 .ui-dialog-offcanvas .ui-dialog-content {
-    -webkit-transition: all .7s ease 2s;
-    -moz-transition: all .7s ease 2s;
-    transition: all .7s ease 2s;
+  -webkit-transition: all .7s ease 2s;
+  -moz-transition: all .7s ease 2s;
+  transition: all .7s ease 2s;
 }
 
 @media (max-width: 700px) {
-    .ui-dialog-offcanvas .ui-dialog-content {
-        -webkit-transition: all .7s ease;
-        -moz-transition: all .7s ease;
-        transition: all .7s ease;
-    }
+  .ui-dialog-offcanvas .ui-dialog-content {
+    -webkit-transition: all .7s ease;
+    -moz-transition: all .7s ease;
+    transition: all .7s ease;
+  }
 }
 
 .dialog-offcanvas__main-canvas {
diff --git a/core/modules/outside_in/css/outside_in.module.css b/core/modules/outside_in/css/outside_in.module.css
index 5ac00ab..2022837 100644
--- a/core/modules/outside_in/css/outside_in.module.css
+++ b/core/modules/outside_in/css/outside_in.module.css
@@ -21,18 +21,3 @@
 #main-canvas.js-outside-in-edit-mode .contextual-links a {
   pointer-events: inherit;
 }
-
-/*
- * Force the tray to be 100% width at the same breakpoint the dialog system uses
- * to expand dialog widths.
- */
-@media all and (max-width: 48em) { /* 768px */
-  .ui-dialog.ui-dialog-offcanvas {
-    width: 100% !important;
-  }
-  /* When tray is at 100% width stop the body from scrolling */
-  .js-tray-open {
-    height: 100%;
-    overflow-y: hidden;
-  }
-}
diff --git a/core/modules/outside_in/css/outside_in.motion.css b/core/modules/outside_in/css/outside_in.motion.css
index 450bffe..1177225 100644
--- a/core/modules/outside_in/css/outside_in.motion.css
+++ b/core/modules/outside_in/css/outside_in.motion.css
@@ -4,10 +4,6 @@
  *
  * Motion effects are in a separate file so that they can be easily turned off
  * to improve performance if desired.
- *
- * @todo Move motion effects file into a core Off-Canvas library and add a
- *   configuration option for browser rendering performance to disable this
- *   file: https://www.drupal.org/node/2784443.
  */
 
 
diff --git a/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php b/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
index b85f8dd..0debdc8 100644
--- a/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
+++ b/core/modules/system/src/Tests/Ajax/OffCanvasDialogTest.php
@@ -13,13 +13,6 @@
 class OffCanvasDialogTest extends AjaxTestBase {
 
   /**
-   * Modules to enable.
-   *
-   * @var array
-   */
-  public static $modules = ['outside_in'];
-
-  /**
    * Test sending AJAX requests to open and manipulate offcanvas dialog.
    */
   public function testDialog() {
diff --git a/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php b/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php
index 9ee8e17..e5fae3d 100644
--- a/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php
+++ b/core/modules/system/tests/modules/offcanvas_test/src/Controller/TestController.php
@@ -55,7 +55,7 @@ public function linksDisplay() {
         ],
         '#attached' => [
           'library' => [
-            'outside_in/drupal.outside_in',
+            'core/drupal.ajax',
           ],
         ],
       ],
@@ -73,7 +73,7 @@ public function linksDisplay() {
         ],
         '#attached' => [
           'library' => [
-            'outside_in/drupal.outside_in',
+            'core/drupal.ajax',
           ],
         ],
       ],
@@ -88,7 +88,7 @@ public function linksDisplay() {
         ],
         '#attached' => [
           'library' => [
-            'outside_in/drupal.outside_in',
+            'core/drupal.ajax',
           ],
         ],
       ],
@@ -131,7 +131,7 @@ public function otherDialogLinks() {
       ],
       '#attached' => [
         'library' => [
-          'outside_in/drupal.outside_in',
+          'core/drupal.ajax',
         ],
       ],
     ];
diff --git a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
index 98c4556..dc4b332 100644
--- a/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
+++ b/core/modules/system/tests/src/FunctionalJavascript/OffCanvasTest.php
@@ -5,7 +5,7 @@
 /**
  * Tests the off-canvas tray functionality.
  *
- * @group outside_in
+ * @group system
  */
 class OffCanvasTest extends OffCanvasTestBase {
 
diff --git a/core/themes/stable/css/core/dialog/offcanvas.css b/core/themes/stable/css/core/dialog/offcanvas.css
index fb671db..0e46c6a 100644
--- a/core/themes/stable/css/core/dialog/offcanvas.css
+++ b/core/themes/stable/css/core/dialog/offcanvas.css
@@ -1,23 +1,39 @@
 /**
  * @file
  * CSS for Offcanvas tray.
- *
- * @todo Move CSS into core dialog library https://www.drupal.org/node/2784443.
  */
 /* Position the dialog-offcanvas tray container outside the right of the viewport. */
 .ui-dialog-offcanvas {
-    box-sizing: border-box;
-    height: 100%;
-    overflow: visible;
+  box-sizing: border-box;
+  height: 100%;
+  overflow: visible;
 }
 
 /* Wrap the form that's inside the dialog-offcanvas tray. */
 .ui-dialog-offcanvas .ui-dialog-content {
-    padding: 0 20px;
-    /* Prevent horizontal scrollbar. */
-    overflow-x: hidden;
-    overflow-y: auto;
+  padding: 0 20px;
+  /* Prevent horizontal scrollbar. */
+  overflow-x: hidden;
+  overflow-y: auto;
 }
+
 [dir="rtl"] .ui-dialog-offcanvas .ui-dialog-content {
-    text-align: right;
+  text-align: right;
+}
+
+/*
+ * Force the tray to be 100% width at the same breakpoint the dialog system uses
+ * to expand dialog widths.
+ */
+@media all and (max-width: 48em) {
+  /* 768px */
+  .ui-dialog.ui-dialog-offcanvas {
+    width: 100% !important;
+  }
+
+  /* When tray is at 100% width stop the body from scrolling */
+  .js-tray-open {
+    height: 100%;
+    overflow-y: hidden;
+  }
 }
diff --git a/core/themes/stable/css/core/dialog/offcanvas.motion.css b/core/themes/stable/css/core/dialog/offcanvas.motion.css
index 1c06994..7228a29 100644
--- a/core/themes/stable/css/core/dialog/offcanvas.motion.css
+++ b/core/themes/stable/css/core/dialog/offcanvas.motion.css
@@ -5,24 +5,23 @@
  * Motion effects are in a separate file so that they can be easily turned off
  * to improve performance if desired.
  *
- * @todo Move motion effects file into a core Off-Canvas library and add a
- *   configuration option for browser rendering performance to disable this
- *   file: https://www.drupal.org/node/2784443.
+ * @todo Add a configuration option for browser rendering performance to disable
+ *   this file: https://www.drupal.org/node/2784443.
  */
 
 /* Transition the dialog-offcanvas tray container, with 2s delay to match main canvas speed. */
 .ui-dialog-offcanvas .ui-dialog-content {
-    -webkit-transition: all .7s ease 2s;
-    -moz-transition: all .7s ease 2s;
-    transition: all .7s ease 2s;
+  -webkit-transition: all .7s ease 2s;
+  -moz-transition: all .7s ease 2s;
+  transition: all .7s ease 2s;
 }
 
 @media (max-width: 700px) {
-    .ui-dialog-offcanvas .ui-dialog-content {
-        -webkit-transition: all .7s ease;
-        -moz-transition: all .7s ease;
-        transition: all .7s ease;
-    }
+  .ui-dialog-offcanvas .ui-dialog-content {
+    -webkit-transition: all .7s ease;
+    -moz-transition: all .7s ease;
+    transition: all .7s ease;
+  }
 }
 
 .dialog-offcanvas__main-canvas {