wp-includes/class-wp-customize-widgets.php:353Ensures widgets are available for all types of previews.
public function schedule_customize_register() { if ( is_admin() ) { $this->customize_register(); } else { add_action( 'wp', array( $this, 'customize_register' ) ); } }Introduced in 3.9.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-customize-widgets.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.