Customizer: Add an `aria-label` attribute to the Add Items button to improve accessibility.

props afercia.
fixes #32713.
Built from https://develop.svn.wordpress.org/trunk@32981


git-svn-id: http://core.svn.wordpress.org/trunk@32952 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-customize-control.php

@@ -1447,7 +1447,7 @@ class WP_Customize_Nav_Menu_Control extends WP_Customize_Control {
 	 */
 	public function content_template() {
 		?>
-		<button type="button" class="button-secondary add-new-menu-item" aria-expanded="false" aria-controls="available-menu-items">
+		<button type="button" class="button-secondary add-new-menu-item" aria-label="<?php esc_attr_e( 'Add or remove menu items' ); ?>" aria-expanded="false" aria-controls="available-menu-items">
 			<?php _e( 'Add Items' ); ?>
 		</button>
 		<button type="button" class="not-a-button reorder-toggle">

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.3-alpha-32980';
+$wp_version = '4.3-alpha-32981';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.