How to enqueue google fonts if we use directly in style.css

I have registered google fonts in my theme function file, then used it in style.css.

function register_google_fonts() {

  wp_register_style( 'googleFonts', 'http://fonts.googleapis.com/css?family=Open+Sans:400,300');
  wp_enqueue_style( 'googleFonts');

}
add_action( 'wp_enqueue_scripts', 'register_google_fonts' );

style.css

.cssClass {

    font-family: 'Open Sans', sans-serif;

}

 

First, theme will try to load the Google font Open Sans if not then use the next font sans-serif