diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class.wp-styles.php
--- a/wp/wp-includes/class.wp-styles.php	Tue Jun 09 11:14:17 2015 +0000
+++ b/wp/wp-includes/class.wp-styles.php	Mon Oct 14 17:39:30 2019 +0200
@@ -1,47 +1,130 @@
 <?php
 /**
- * BackPress Styles enqueue.
+ * Dependencies API: WP_Styles class
  *
- * These classes were refactored from the WordPress WP_Scripts and WordPress
- * script enqueue API.
+ * @since 2.6.0
  *
- * @package BackPress
- * @since r74
+ * @package WordPress
+ * @subpackage Dependencies
  */
 
 /**
- * BackPress Styles enqueue class.
+ * Core class used to register styles.
  *
- * @package BackPress
- * @uses WP_Dependencies
- * @since r74
+ * @since 2.6.0
+ *
+ * @see WP_Dependencies
  */
 class WP_Styles extends WP_Dependencies {
+	/**
+	 * Base URL for styles.
+	 *
+	 * Full URL with trailing slash.
+	 *
+	 * @since 2.6.0
+	 * @var string
+	 */
 	public $base_url;
+
+	/**
+	 * URL of the content directory.
+	 *
+	 * @since 2.8.0
+	 * @var string
+	 */
 	public $content_url;
+
+	/**
+	 * Default version string for stylesheets.
+	 *
+	 * @since 2.6.0
+	 * @var string
+	 */
 	public $default_version;
+
+	/**
+	 * The current text direction.
+	 *
+	 * @since 2.6.0
+	 * @var string
+	 */
 	public $text_direction = 'ltr';
+
+	/**
+	 * Holds a list of style handles which will be concatenated.
+	 *
+	 * @since 2.8.0
+	 * @var string
+	 */
 	public $concat = '';
+
+	/**
+	 * Holds a string which contains style handles and their version.
+	 *
+	 * @since 2.8.0
+	 * @deprecated 3.4.0
+	 * @var string
+	 */
 	public $concat_version = '';
+
+	/**
+	 * Whether to perform concatenation.
+	 *
+	 * @since 2.8.0
+	 * @var bool
+	 */
 	public $do_concat = false;
+
+	/**
+	 * Holds HTML markup of styles and additional data if concatenation
+	 * is enabled.
+	 *
+	 * @since 2.8.0
+	 * @var string
+	 */
 	public $print_html = '';
+
+	/**
+	 * Holds inline styles if concatenation is enabled.
+	 *
+	 * @since 3.3.0
+	 * @var string
+	 */
 	public $print_code = '';
+
+	/**
+	 * List of default directories.
+	 *
+	 * @since 2.8.0
+	 * @var array
+	 */
 	public $default_dirs;
 
+	/**
+	 * Constructor.
+	 *
+	 * @since 2.6.0
+	 */
 	public function __construct() {
 		/**
 		 * Fires when the WP_Styles instance is initialized.
 		 *
 		 * @since 2.6.0
 		 *
-		 * @param WP_Styles &$this WP_Styles instance, passed by reference.
+		 * @param WP_Styles $this WP_Styles instance (passed by reference).
 		 */
 		do_action_ref_array( 'wp_default_styles', array(&$this) );
 	}
 
 	/**
-	 * @param string $handle
-	 * @return bool
+	 * Processes a style dependency.
+	 *
+	 * @since 2.6.0
+	 *
+	 * @see WP_Dependencies::do_item()
+	 *
+	 * @param string $handle The style's registered handle.
+	 * @return bool True on success, false on failure.
 	 */
 	public function do_item( $handle ) {
 		if ( !parent::do_item($handle) )
@@ -72,23 +155,40 @@
 		else
 			$media = 'all';
 
-		$href = $this->_css_href( $obj->src, $ver, $handle );
-		if ( empty( $href ) ) {
-			// Turns out there is nothing to print.
+		// A single item may alias a set of items, by having dependencies, but no source.
+		if ( ! $obj->src ) {
+			if ( $inline_style = $this->print_inline_style( $handle, false ) ) {
+				$inline_style = sprintf( "<style id='%s-inline-css' type='text/css'>\n%s\n</style>\n", esc_attr( $handle ), $inline_style );
+				if ( $this->do_concat ) {
+					$this->print_html .= $inline_style;
+				} else {
+					echo $inline_style;
+				}
+			}
 			return true;
 		}
+
+		$href = $this->_css_href( $obj->src, $ver, $handle );
+		if ( ! $href ) {
+			return true;
+		}
+
 		$rel = isset($obj->extra['alt']) && $obj->extra['alt'] ? 'alternate stylesheet' : 'stylesheet';
 		$title = isset($obj->extra['title']) ? "title='" . esc_attr( $obj->extra['title'] ) . "'" : '';
 
 		/**
-		 * Filter the HTML link tag of an enqueued style.
+		 * Filters the HTML link tag of an enqueued style.
 		 *
 		 * @since 2.6.0
+		 * @since 4.3.0 Introduced the `$href` parameter.
+		 * @since 4.5.0 Introduced the `$media` parameter.
 		 *
-		 * @param string         The link tag for the enqueued style.
+		 * @param string $html   The link tag for the enqueued style.
 		 * @param string $handle The style's registered handle.
+		 * @param string $href   The stylesheet's source URL.
+		 * @param string $media  The stylesheet's media attribute.
 		 */
-		$tag = apply_filters( 'style_loader_tag', "<link rel='$rel' id='$handle-css' $title href='$href' type='text/css' media='$media' />\n", $handle );
+		$tag = apply_filters( 'style_loader_tag', "<link rel='$rel' id='$handle-css' $title href='$href' type='text/css' media='$media' />\n", $handle, $href, $media);
 		if ( 'rtl' === $this->text_direction && isset($obj->extra['rtl']) && $obj->extra['rtl'] ) {
 			if ( is_bool( $obj->extra['rtl'] ) || 'replace' === $obj->extra['rtl'] ) {
 				$suffix = isset( $obj->extra['suffix'] ) ? $obj->extra['suffix'] : '';
@@ -98,7 +198,7 @@
 			}
 
 			/** This filter is documented in wp-includes/class.wp-styles.php */
-			$rtl_tag = apply_filters( 'style_loader_tag', "<link rel='$rel' id='$handle-rtl-css' $title href='$rtl_href' type='text/css' media='$media' />\n", $handle );
+			$rtl_tag = apply_filters( 'style_loader_tag', "<link rel='$rel' id='$handle-rtl-css' $title href='$rtl_href' type='text/css' media='$media' />\n", $handle, $rtl_href, $media );
 
 			if ( $obj->extra['rtl'] === 'replace' ) {
 				$tag = $rtl_tag;
@@ -131,8 +231,13 @@
 	}
 
 	/**
-	 * @param string $handle
-	 * @param string $code
+	 * Adds extra CSS styles to a registered stylesheet.
+	 *
+	 * @since 3.3.0
+	 *
+	 * @param string $handle The style's registered handle.
+	 * @param string $code   String containing the CSS styles to be added.
+	 * @return bool True on success, false on failure.
 	 */
 	public function add_inline_style( $handle, $code ) {
 		if ( ! $code ) {
@@ -150,9 +255,14 @@
 	}
 
 	/**
-	 * @param string $handle
-	 * @param bool $echo
-	 * @return bool
+	 * Prints extra CSS styles of a registered stylesheet.
+	 *
+	 * @since 3.3.0
+	 *
+	 * @param string $handle The style's registered handle.
+	 * @param bool   $echo   Optional. Whether to echo the inline style instead of just returning it.
+	 *                       Default true.
+	 * @return string|bool False if no data exists, inline styles if `$echo` is true, true otherwise.
 	 */
 	public function print_inline_style( $handle, $echo = true ) {
 		$output = $this->get_data( $handle, 'after' );
@@ -173,16 +283,22 @@
 	}
 
 	/**
-	 * @param mixed $handles
-	 * @param bool $recursion
-	 * @param mixed $group
-	 * @return bool
+	 * Determines style dependencies.
+	 *
+	 * @since 2.6.0
+	 *
+	 * @see WP_Dependencies::all_deps()
+	 *
+	 * @param mixed     $handles   Item handle and argument (string) or item handles and arguments (array of strings).
+	 * @param bool      $recursion Internal flag that function is calling itself.
+	 * @param int|false $group     Group level: (int) level, (false) no groups.
+	 * @return bool True on success, false on failure.
 	 */
 	public function all_deps( $handles, $recursion = false, $group = false ) {
-		$r = parent::all_deps( $handles, $recursion );
-		if ( !$recursion ) {
+		$r = parent::all_deps( $handles, $recursion, $group );
+		if ( ! $recursion ) {
 			/**
-			 * Filter the array of enqueued styles before processing for output.
+			 * Filters the array of enqueued styles before processing for output.
 			 *
 			 * @since 2.6.0
 			 *
@@ -194,10 +310,14 @@
 	}
 
 	/**
-	 * @param string $src
-	 * @param string $ver
-	 * @param string $handle
-	 * @return string
+	 * Generates an enqueued style's fully-qualified URL.
+	 *
+	 * @since 2.6.0
+	 *
+	 * @param string $src The source of the enqueued style.
+	 * @param string $ver The version of the enqueued style.
+	 * @param string $handle The style's registered handle.
+	 * @return string Style's fully-qualified URL.
 	 */
 	public function _css_href( $src, $ver, $handle ) {
 		if ( !is_bool($src) && !preg_match('|^(https?:)?//|', $src) && ! ( $this->content_url && 0 === strpos($src, $this->content_url) ) ) {
@@ -208,7 +328,7 @@
 			$src = add_query_arg('ver', $ver, $src);
 
 		/**
-		 * Filter an enqueued style's fully-qualified URL.
+		 * Filters an enqueued style's fully-qualified URL.
 		 *
 		 * @since 2.6.0
 		 *
@@ -220,10 +340,14 @@
 	}
 
 	/**
-	 * @param string $src
-	 * @return bool
+	 * Whether a handle's source is in a default directory.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @param string $src The source of the enqueued style.
+	 * @return bool True if found, false if not.
 	 */
-	public function in_default_dir($src) {
+	public function in_default_dir( $src ) {
 		if ( ! $this->default_dirs )
 			return true;
 
@@ -234,11 +358,27 @@
 		return false;
 	}
 
-	public function do_footer_items() { // HTML 5 allows styles in the body, grab late enqueued items and output them in the footer.
+	/**
+	 * Processes items and dependencies for the footer group.
+	 *
+	 * HTML 5 allows styles in the body, grab late enqueued items and output them in the footer.
+	 *
+	 * @since 3.3.0
+	 *
+	 * @see WP_Dependencies::do_items()
+	 *
+	 * @return array Handles of items that have been processed.
+	 */
+	public function do_footer_items() {
 		$this->do_items(false, 1);
 		return $this->done;
 	}
 
+	/**
+	 * Resets class properties.
+	 *
+	 * @since 3.3.0
+	 */
 	public function reset() {
 		$this->do_concat = false;
 		$this->concat = '';