    /**
     * @class Ext.grid.feature.Chunking
     * @extends Ext.grid.feature.Feature
     */
    Ext.define('Ext.grid.feature.Chunking', {
        extend: 'Ext.grid.feature.Feature',
        alias: 'feature.chunking',

        chunkSize: 20,
        rowHeight: Ext.isIE ? 27 : 26,
        visibleChunk: 0,
        hasFeatureEvent: false,
        attachEvents: function() {
            var grid = this.view.up('gridpanel'),
                scroller = grid.down('gridscroller[dock=right]');
            scroller.el.on('scroll', this.onBodyScroll, this, {buffer: 300});
            //this.view.on('bodyscroll', this.onBodyScroll, this, {buffer: 300});
        },

        onBodyScroll: function(e, t) {
            var view = this.view,
                top  = t.scrollTop,
                nextChunk = Math.floor(top / this.rowHeight / this.chunkSize);
            if (nextChunk !== this.visibleChunk) {

                this.visibleChunk = nextChunk;
                view.refresh();
                view.el.dom.scrollTop = top;
                //BrowserBug: IE6,7,8 quirks mode takes setting scrollTop 2x.
                view.el.dom.scrollTop = top;
            }
        },

        collectData: function(records, preppedRecords, startIndex, fullWidth, orig) {
            var o = {
                fullWidth: orig.fullWidth,
                chunks: []
            },
            //headerCt = this.view.headerCt,
            //colums = headerCt.getColumnsForTpl(),
            recordCount = orig.rows.length,
            start = 0,
            i = 0,
            visibleChunk = this.visibleChunk,
            chunk,
            rows,
            chunkLength;

            for (; start < recordCount; start+=this.chunkSize, i++) {
                if (start+this.chunkSize > recordCount) {
                    chunkLength = recordCount - start;
                } else {
                    chunkLength = this.chunkSize;
                }

                if (i >= visibleChunk - 1 && i <= visibleChunk + 1) {
                    rows = orig.rows.slice(start, start+this.chunkSize);
                } else {
                    rows = [];
                }
                o.chunks.push({
                    rows: rows,
                    fullWidth: fullWidth,
                    chunkHeight: chunkLength * this.rowHeight
                });
            }

            return o;
        },

        getTableFragments: function() {
            return {
                openTableWrap: function() {
                    return '<tpl for="chunks"><div class="' + Ext.baseCSSPrefix + 'grid-chunk" style="height: {chunkHeight}px;">';
                },
                closeTableWrap: function() {
                    return '</div></tpl>';
                }
            };
        }
    });