Index: src/wp-admin/includes/class-wp-upgrader-skins.php
===================================================================
--- src/wp-admin/includes/class-wp-upgrader-skins.php	(revision 35724)
+++ src/wp-admin/includes/class-wp-upgrader-skins.php	(working copy)
@@ -224,7 +224,8 @@
 	public function after() {
 		$this->plugin = $this->upgrader->plugin_info();
 		if ( !empty($this->plugin) && !is_wp_error($this->result) && $this->plugin_active ){
-			echo '<iframe style="border:0;overflow:hidden" width="100%" height="170px" src="' . wp_nonce_url('update.php?action=activate-plugin&networkwide=' . $this->plugin_network_active . '&plugin=' . urlencode( $this->plugin ), 'activate-plugin_' . $this->plugin) .'"></iframe>';
+			// Currently used only when JS is off for a single plugin update?
+			echo '<iframe title="' . esc_attr( 'Updating...' ) . '" style="border:0;overflow:hidden" width="100%" height="170" src="' . wp_nonce_url( 'update.php?action=activate-plugin&networkwide=' . $this->plugin_network_active . '&plugin=' . urlencode( $this->plugin ), 'activate-plugin_' . $this->plugin ) . '"></iframe>';
 		}
 
 		$this->decrement_update_count( 'plugin' );
Index: src/wp-admin/update-core.php
===================================================================
--- src/wp-admin/update-core.php	(revision 35724)
+++ src/wp-admin/update-core.php	(working copy)
@@ -644,7 +644,7 @@
 	require_once(ABSPATH . 'wp-admin/admin-header.php');
 	echo '<div class="wrap">';
 	echo '<h1>' . __( 'Update Plugins' ) . '</h1>';
-	echo '<iframe src="', $url, '" style="width: 100%; height: 100%; min-height: 750px;" frameborder="0"></iframe>';
+	echo '<iframe src="', $url, '" style="width: 100%; height: 100%; min-height: 750px;" frameborder="0" title="' . esc_attr( 'Updating...' ) . '"></iframe>';
 	echo '</div>';
 	include(ABSPATH . 'wp-admin/admin-footer.php');
 
@@ -673,7 +673,7 @@
 	?>
 	<div class="wrap">
 		<h1><?php _e( 'Update Themes' ); ?></h1>
-		<iframe src="<?php echo $url ?>" style="width: 100%; height: 100%; min-height: 750px;" frameborder="0"></iframe>
+		<iframe src="<?php echo $url ?>" style="width: 100%; height: 100%; min-height: 750px;" frameborder="0" title="<?php esc_attr_e( 'Updating...' ); ?>"></iframe>
 	</div>
 	<?php
 	include(ABSPATH . 'wp-admin/admin-footer.php');