Add Page dropdown to Gravity Views

/* Filter search criteria */
add_filter( 'gravityview_search_criteria', function( $criteria ) {
    if( isset($_GET['custom_count']) ) {
        $criteria['paging']['page_size'] = $_GET['custom_count'];
    };
    return $criteria;
} );

/*
* Create Shortcode
* Usage: [gv_custom_page_dropdown]
*/
add_shortcode('gv_custom_page_dropdown', 'gv_custom_page_dropdown');
function gv_custom_page_dropdown($atts) {

    global $gravityview_view;

    $pagination_counts = $gravityview_view->getPaginationCounts();

    $total = $pagination_counts['total'];
    $last = $pagination_counts['last'];

    $minimum_posts_per_page = isset($atts['minimum-posts-per-page']) ? $atts['minimum-posts-per-page'] : 25;
    if($total <= $minimum_posts_per_page) {
        return;
    }

    $current_posts_per_page = isset($_GET['custom_count']) ? intval($_GET['custom_count']) : $minimum_posts_per_page;

    // Begin posts_per_page dropdown
    $customDropdown ='<form method="get" class="form-inline">';
    $customDropdown .='<select class="btn btn-default" name="custom_count">';
        // Create all custom options below total
        $x = $minimum_posts_per_page;
        while($x < $total) {
            $customDropdown .= "<option value='$x'";
            if($x == $current_posts_per_page) {
                $customDropdown .=  ' selected';
            }
            $customDropdown .= ">$x</option>";
            $x *= 2;
        }
        // Create final option
        $customDropdown .= "<option value='$x'";
        if($x == $current_posts_per_page) {
            $customDropdown .=  ' selected';
        }
        $customDropdown .= ">$x</option>";

    $customDropdown .= '</select>';

    $customDropdown .='<input type="submit" class="btn btn-xs btn-primary" value="Update" />';
    $customDropdown .='</form>';

    return $customDropdown;
}