Index: src/wp-includes/css/wp-auth-check.css
===================================================================
--- src/wp-includes/css/wp-auth-check.css	(revision 35983)
+++ src/wp-includes/css/wp-auth-check.css	(working copy)
@@ -87,35 +87,26 @@

 #wp-auth-check-wrap .wp-auth-check-close {
 	position: absolute;
-	top: 8px;
-	right: 8px;
+	top: 5px;
+	right: 5px;
 	height: 22px;
 	width: 22px;
-	cursor: pointer;
+	color: #72777c;
 }

 #wp-auth-check-wrap .wp-auth-check-close:before {
 	content: "\f158";
-	display: block !important;
-	font: normal 20px/1 dashicons;
+	font: normal 20px/22px dashicons;
 	speak: none;
-	height: 22px;
-	margin: 2px 0;
-	text-align: center;
-	width: 22px;
-	color: #777;
 	-webkit-font-smoothing: antialiased !important;
 	-moz-osx-font-smoothing: grayscale;
 }

-#wp-auth-check-wrap .wp-auth-check-close:hover:before {
+#wp-auth-check-wrap .wp-auth-check-close:hover,
+#wp-auth-check-wrap .wp-auth-check-close:focus {
 	color: #0073aa;
 }

-#wp-auth-check-wrap .wp-auth-check-close:focus {
-	outline: 1px dotted #82878c;
-}
-
 #wp-auth-check-wrap .wp-auth-fallback-expired {
 	outline: 0;
 }
Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 35983)
+++ src/wp-includes/functions.php	(working copy)
@@ -4934,7 +4934,7 @@
 	<div id="wp-auth-check-wrap" class="<?php echo $wrap_class; ?>">
 	<div id="wp-auth-check-bg"></div>
 	<div id="wp-auth-check">
-	<div class="wp-auth-check-close" tabindex="0" title="<?php esc_attr_e('Close'); ?>"></div>
+	<button type="button" class="wp-auth-check-close button-link"><span class="screen-reader-text"><?php _e( 'Close dialog' ); ?></span></button>
 	<?php

 	if ( $same_domain ) {