Added SerialColumn.

framework/yii/widgets/grid/SerialColumn.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\widgets\grid;
+
+/**
+ * SerialColumn displays a column of row numbers (1-based).
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class SerialColumn extends Column
+{
+	/**
+	 * Renders the data cell content.
+	 * @param mixed $model the data model
+	 * @param integer $index the zero-based index of the data model among the models array returned by [[dataProvider]].
+	 * @return string the rendering result
+	 */
+	protected function renderDataCellContent($model, $index)
+	{
+		$pagination = $this->grid->dataProvider->getPagination();
+		if ($pagination !== false) {
+			return $pagination->getOffset() + $index + 1;
+		} else {
+			return $index + 1;
+		}
+	}
+}