multi page gravity form dynamic population isn’t working properly

What’s the best way to dynamically populate a multi page form?

add_filter("gform_field_value_source", "populate_form");
function populate_form($value){
    $key = 'source';
    $value = 'source is not set.';

    if ( ! isset( $_REQUEST[ $key ] ) || empty( $_REQUEST[ $key ] ) ) {
        $value = 'Cookie value is ' . $_COOKIE['source'];
    }else{
        $value = 'Request value is ' . strip_tags( (string) wp_unslash( $_REQUEST[ $key ] ) );
    }
    return $value;  
}

This is working perfectly in Google Chrome but it doesn’t work in Firefox. What is missing to make it work across multiple browser?