Accessibility: Media: Add an `aria-pressed` attribute to active button within a button group.

The `aria-pressed` attribute communicates semantically the "active" state of buttons that otherwise only look "active".

Props afercia.
Merges [46748] to the 5.3 branch.
Fixes #48355.
Built from https://develop.svn.wordpress.org/branches/5.3@46778


git-svn-id: http://core.svn.wordpress.org/branches/5.3@46578 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/media-views.js

@@ -8758,8 +8758,12 @@ Settings = View.extend(/** @lends wp.media.view.Settings.prototype */{
 
 		// Handle button groups.
 		} else if ( $setting.hasClass('button-group') ) {
-			$buttons = $setting.find('button').removeClass('active');
-			$buttons.filter( '[value="' + value + '"]' ).addClass('active');
+			$buttons = $setting.find( 'button' )
+				.removeClass( 'active' )
+				.attr( 'aria-pressed', 'false' );
+			$buttons.filter( '[value="' + value + '"]' )
+				.addClass( 'active' )
+				.attr( 'aria-pressed', 'true' );
 
 		// Handle text inputs and textareas.
 		} else if ( $setting.is('input[type="text"], textarea') ) {

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3.1-alpha-46777';
+$wp_version = '5.3.1-alpha-46778';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.