diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/customize/class-wp-widget-form-customize-control.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/customize/class-wp-widget-form-customize-control.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,80 @@
+<?php
+/**
+ * Customize API: WP_Widget_Form_Customize_Control class
+ *
+ * @package WordPress
+ * @subpackage Customize
+ * @since 4.4.0
+ */
+
+/**
+ * Widget Form Customize Control class.
+ *
+ * @since 3.9.0
+ *
+ * @see WP_Customize_Control
+ */
+class WP_Widget_Form_Customize_Control extends WP_Customize_Control {
+	public $type = 'widget_form';
+	public $widget_id;
+	public $widget_id_base;
+	public $sidebar_id;
+	public $is_new = false;
+	public $width;
+	public $height;
+	public $is_wide = false;
+
+	/**
+	 * Gather control params for exporting to JavaScript.
+	 *
+	 * @since 3.9.0
+	 *
+	 * @global array $wp_registered_widgets
+	 */
+	public function to_json() {
+		global $wp_registered_widgets;
+
+		parent::to_json();
+		$exported_properties = array( 'widget_id', 'widget_id_base', 'sidebar_id', 'width', 'height', 'is_wide' );
+		foreach ( $exported_properties as $key ) {
+			$this->json[ $key ] = $this->$key;
+		}
+
+		// Get the widget_control and widget_content.
+		require_once ABSPATH . '/wp-admin/includes/widgets.php';
+
+		$widget = $wp_registered_widgets[ $this->widget_id ];
+		if ( ! isset( $widget['params'][0] ) ) {
+			$widget['params'][0] = array();
+		}
+
+		$args = array(
+			'widget_id' => $widget['id'],
+			'widget_name' => $widget['name'],
+		);
+
+		$args = wp_list_widget_controls_dynamic_sidebar( array( 0 => $args, 1 => $widget['params'][0] ) );
+		$widget_control_parts = $this->manager->widgets->get_widget_control_parts( $args );
+
+		$this->json['widget_control'] = $widget_control_parts['control'];
+		$this->json['widget_content'] = $widget_control_parts['content'];
+	}
+
+	/**
+	 * Override render_content to be no-op since content is exported via to_json for deferred embedding.
+	 *
+	 * @since 3.9.0
+	 */
+	public function render_content() {}
+
+	/**
+	 * Whether the current widget is rendered on the page.
+	 *
+	 * @since 4.0.0
+	 *
+	 * @return bool Whether the widget is rendered.
+	 */
+	public function active_callback() {
+		return $this->manager->widgets->is_widget_rendered( $this->widget_id );
+	}
+}