Ticket #40185: 40185.patch

src/wp-admin/includes/meta-boxes.php

@@ -50 +50 @@
 <?php
 $preview_link = esc_url( get_preview_post_link( $post ) );
 if ( 'publish' == $post->post_status ) {
-        $preview_button = __( 'Preview Changes' );
+        $preview_button_text = __( 'Preview Changes' );
 } else {
-        $preview_button = __( 'Preview' );
+        $preview_button_text = __( 'Preview' );
 }
+$preview_button = sprintf( '%1$s<span class="screen-reader-text"> %2$s</span>',
+                            esc_html( $preview_button_text ),
+                            esc_html__( '(link opens in a new window)' ) );
 ?>
 <a class="preview button" href="<?php echo $preview_link; ?>" target="wp-preview-<?php echo (int) $post->ID; ?>" id="post-preview"><?php echo $preview_button; ?></a>
 <input type="hidden" name="wp-preview" id="wp-preview" value="" />