_remove_theme_support( string $feature )

function _remove_theme_support( $feature ) {
	global $_wp_theme_features;

	switch ( $feature ) {
		case 'custom-header-uploads' :
			if ( ! isset( $_wp_theme_features['custom-header'] ) )
				return false;
			add_theme_support( 'custom-header', array( 'uploads' => false ) );
			return; // Do not continue - custom-header-uploads no longer exists.
	}

	if ( ! isset( $_wp_theme_features[ $feature ] ) )
		return false;

	switch ( $feature ) {
		case 'custom-header' :
			if ( ! did_action( 'wp_loaded' ) )
				break;
			$support = get_theme_support( 'custom-header' );
			if ( isset( $support[0]['wp-head-callback'] ) ) {
				remove_action( 'wp_head', $support[0]['wp-head-callback'] );
			}
			if ( isset( $GLOBALS['custom_image_header'] ) ) {
				remove_action( 'admin_menu', array( $GLOBALS['custom_image_header'], 'init' ) );
				unset( $GLOBALS['custom_image_header'] );
			}
			break;

		case 'custom-background' :
			if ( ! did_action( 'wp_loaded' ) )
				break;
			$support = get_theme_support( 'custom-background' );
			remove_action( 'wp_head', $support[0]['wp-head-callback'] );
			remove_action( 'admin_menu', array( $GLOBALS['custom_background'], 'init' ) );
			unset( $GLOBALS['custom_background'] );
			break;
	}

	unset( $_wp_theme_features[ $feature ] );
	return true;
}