Index: wp-admin/includes/class-wp-list-table.php
===================================================================
--- wp-admin/includes/class-wp-list-table.php	(revision 21256)
+++ wp-admin/includes/class-wp-list-table.php	(working copy)
@@ -664,6 +664,13 @@
 		else
 			$current_order = 'asc';
 
+		if ( ! empty( $columns['cb'] ) ) {
+			static $cb_counter = 1;
+			$columns['cb'] = '<label class="screen-reader-text" for="cb-select-all-' . $cb_counter . '">' . __( 'Select All' )
+				. '</label><input id="cb-select-all-' . $cb_counter . '" type="checkbox" />';
+			$cb_counter++;
+		}
+
 		foreach ( $columns as $column_key => $column_display_name ) {
 			$class = array( 'manage-column', "column-$column_key" );