Source

File: wp-includes/class-wp-customize-widgets.php

public function __construct( $manager ) {
		$this->manager = $manager;

		// See https://github.com/xwp/wp-customize-snapshots/blob/962586659688a5b1fd9ae93618b7ce2d4e7a421c/php/class-customize-snapshot-manager.php#L420-L449
		add_filter( 'customize_dynamic_setting_args', array( $this, 'filter_customize_dynamic_setting_args' ), 10, 2 );
		add_action( 'widgets_init', array( $this, 'register_settings' ), 95 );
		add_action( 'customize_register', array( $this, 'schedule_customize_register' ), 1 );

		// Skip remaining hooks when the user can't manage widgets anyway.
		if ( ! current_user_can( 'edit_theme_options' ) ) {
			return;
		}

		add_action( 'wp_loaded', array( $this, 'override_sidebars_widgets_for_theme_switch' ) );
		add_action( 'customize_controls_init', array( $this, 'customize_controls_init' ) );
		add_action( 'customize_controls_enqueue_scripts', array( $this, 'enqueue_scripts' ) );
		add_action( 'customize_controls_print_styles', array( $this, 'print_styles' ) );
		add_action( 'customize_controls_print_scripts', array( $this, 'print_scripts' ) );
		add_action( 'customize_controls_print_footer_scripts', array( $this, 'print_footer_scripts' ) );
		add_action( 'customize_controls_print_footer_scripts', array( $this, 'output_widget_control_templates' ) );
		add_action( 'customize_preview_init', array( $this, 'customize_preview_init' ) );
		add_filter( 'customize_refresh_nonces', array( $this, 'refresh_nonces' ) );

		add_action( 'dynamic_sidebar', array( $this, 'tally_rendered_widgets' ) );
		add_filter( 'is_active_sidebar', array( $this, 'tally_sidebars_via_is_active_sidebar_calls' ), 10, 2 );
		add_filter( 'dynamic_sidebar_has_widgets', array( $this, 'tally_sidebars_via_dynamic_sidebar_calls' ), 10, 2 );

		// Selective Refresh.
		add_filter( 'customize_dynamic_partial_args', array( $this, 'customize_dynamic_partial_args' ), 10, 2 );
		add_action( 'customize_preview_init', array( $this, 'selective_refresh_init' ) );
	}