KSES: Support `'tag' => true` as a shorthand for `'tag' => array()` in `wp_kses_attr()`.

`Automatic_Upgrader_Skin::feedback()` had always assumed that this is already the case, now it is.

See #20017.
Fixes #40680.
Built from https://develop.svn.wordpress.org/trunk@40637


git-svn-id: http://core.svn.wordpress.org/trunk@40498 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/kses.php

@@ -828,8 +828,9 @@ function wp_kses_attr($element, $attr, $allowed_html, $allowed_protocols) {
 		$xhtml_slash = ' /';
 
 	// Are any attributes allowed at all for this element?
-	if ( ! isset($allowed_html[strtolower($element)]) || count($allowed_html[strtolower($element)]) == 0 )
+	if ( ! isset( $allowed_html[ strtolower( $element ) ] ) || true === $allowed_html[ strtolower( $element ) ] || count( $allowed_html[ strtolower( $element ) ] ) == 0 ) {
 		return "<$element$xhtml_slash>";
+	}
 
 	// Split it
 	$attrarr = wp_kses_hair($attr, $allowed_protocols);

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-alpha-40636';
+$wp_version = '4.8-alpha-40637';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.