Script Loader: Do not normalize absolute paths in inline block styles CSS.

`_wp_normalize_relative_css_links()` used to normalize all non-absolute URLs regardless of whether it's a relative path or an absolute path. The normalization should only happen for relative paths (paths without a leading `/`) and not for absolute paths.

Reference: [https://www.rfc-editor.org/rfc/rfc1808#section-4 RFC 1808, Section 4, Step 4].

Follow-up to [52036], [52695], [52754], [55658], [55669].

Props scholdstrom.
Fixes #61909.

git-svn-id: https://develop.svn.wordpress.org/trunk@58932 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/script-loader.php

@@ -3056,7 +3056,7 @@ static function ( $matches ) use ( $stylesheet_url ) {
 			if (
 				str_starts_with( $url, 'http:' ) ||
 				str_starts_with( $url, 'https:' ) ||
-				str_starts_with( $url, '//' ) ||
+				str_starts_with( $url, '/' ) ||
 				str_starts_with( $url, '#' ) ||
 				str_starts_with( $url, 'data:' )
 			) {

tests/phpunit/tests/dependencies/styles.php

@@ -228,6 +228,10 @@ public function data_normalize_relative_css_links() {
 				'css'      => 'p {background-image: url(\'../image1.jpg\');}',
 				'expected' => 'p {background-image: url(\'/wp-content/themes/test/../image1.jpg\');}',
 			),
+			'URLs with absolute path, shouldn\'t change'   => array(
+				'css'      => 'p {background:url( "/image0.svg" );}',
+				'expected' => 'p {background:url( "/image0.svg" );}',
+			),
 			'External URLs, shouldn\'t change'             => array(
 				'css'      => 'p {background-image: url(\'http://foo.com/image2.png\');}',
 				'expected' => 'p {background-image: url(\'http://foo.com/image2.png\');}',