Method: Prevents sending a 404 status when returning the response for the customize preview, since it causes the jQuery Ajax to fail. Send 200 instead.
Source: wp-includes/class-wp-customize-manager.php:2014
Method: Prints JavaScript settings for preview frame.
Source: wp-includes/class-wp-customize-manager.php:2109
Method: Prints a signature so we can ensure the Customizer was properly executed.
Source: wp-includes/class-wp-customize-manager.php:2229
Method: Dismisses all of the current user’s auto-drafts (other than the present one).
Source: wp-includes/class-wp-customize-manager.php:1060
Method: Returns true if it’s an Ajax request.
Source: wp-includes/class-wp-customize-manager.php:419
Method: Enqueues scripts for customize controls.
Source: wp-includes/class-wp-customize-manager.php:4536
Method: Establishes the loaded changeset.
Source: wp-includes/class-wp-customize-manager.php:613
Method: Exports header video settings to facilitate selective refresh.
Source: wp-includes/class-wp-customize-manager.php:6052
Method: Filters the X-Frame-Options and Content-Security-Policy headers to ensure frontend can load in customizer.
Source: wp-includes/class-wp-customize-manager.php:1957
Method: Finds the changeset post ID for a given changeset UUID.
Source: wp-includes/class-wp-customize-manager.php:977