gistfile1.php

<?php

// Wrong 1
<link href='http://fonts.googleapis.com/css?family=Cabin:400,500|Open+Sans:300,400,700|Oswald:300,400,700|PT+Sans+Caption:400,700' rel='stylesheet' type='text/css'>

// Wrong 2

/**
 * Enqueue the Open Sans font.
 */
function mytheme_fonts() {
    $protocol = is_ssl() ? 'https' : 'http';
    wp_enqueue_style( 'mytheme-opensans', "$protocol://fonts.googleapis.com/css?family=Open+Sans" );}
add_action( 'wp_enqueue_scripts', 'mytheme_fonts' );

// ## Correct

/**
 * Register custom fonts.
 */
function my_theme_fonts_url() {
	$fonts_url = '';

	$libre_franklin = _x( 'on', 'libre_franklin font: on or off', 'twentyseventeen' );

	if ( 'off' !== $libre_franklin ) {
		$font_families = array();

		$font_families[] = 'Libre Franklin:300,300i,400,400i,600,600i,800,800i';

		$query_args = array(
			'family' => urlencode( implode( '|', $font_families ) ),
			'subset' => urlencode( 'latin,latin-ext' ),
		);

		$fonts_url = add_query_arg( $query_args, 'https://fonts.googleapis.com/css' );
	}

	return esc_url_raw( $fonts_url );
}

/**
 * Enqueue scripts and styles.
 */
function my_theme_custom_scripts() {
	// Add custom fonts, used in the main stylesheet.
	wp_enqueue_style( 'my-theme-fonts', my_theme_fonts_url(), array(), null );
}
add_action( 'wp_enqueue_scripts', 'my_theme_custom_scripts' );

function my_theme_resource_hints( $urls, $relation_type ) {
	if ( wp_style_is( 'my-theme-fonts', 'queue' ) && 'preconnect' === $relation_type ) {
		$urls[] = array(
			'href' => 'https://fonts.gstatic.com',
			'crossorigin',
		);
	}

	return $urls;
}
add_filter( 'wp_resource_hints', 'my_theme_resource_hints', 10, 2 );