title: ExtJS Grid renders more rows than specified in pagesize
body: <p>I have implemented an infinite grid based on the example given by Sencha. Basically the proxy fetches json files using jsonp and populates the grid. I want the grid size to be 10 and I want the proxy to make subsequent requests only when the user scrolls down closer to the 10th record. Each record takes sufficient space vertically in the grid view, and only about 5 records can be seen without scrolling (on my 14 inch laptop with a resolution of 1366 x 768). I have set the pagesize to be 10, and my expectation is that the grid refreshes only when I scroll down beyond the visible records. However, the grid loads all the data (50 records in all) by making 5 individual requests even without scrolling.  Here's the code:</p>
  
  <pre><code>Ext.require([
      'Ext.grid.*',
      'Ext.data.*',
      'Ext.util.*',
      'Ext.grid.plugin.BufferedRenderer'
  ]);
  
  Ext.onReady(function() {
      Ext.define('ContentModel', {
          extend : 'Ext.data.Model',
          fields : [ 'content_id', 'content' ],
          idProperty: 'content_id'
      });
  
      var store = Ext.create('Ext.data.Store', {
          id : 'store',
          model : 'ContentModel',
          buffered: true,
          pageSize: 10,
          proxy : {
              type : 'jsonp',
              url : 'http://website.com/Top1.json',
              reader: {
                  root: 'contents',
                  totalProperty: 'totalCount'
              }
          },
          autoLoad : true
      });
  
      var grid = Ext.create('Ext.grid.Panel', {
          renderTo : Ext.getBody(),
          width : '100%',
          height : '100%',
          title : 'Reader Panel',
          id : 'reader',
          store : store,
          columns : [ {
              id : 'content_id',
              text : 'Content ID',
              dataIndex : 'content_id',
              width : '10%'
          },
          {
              id : 'content',
              text : 'Content',
              dataIndex : 'content',
              width : '90%'
          } ]
      });
  
      Ext.define('JSONP Proxy', {
          override: 'Ext.data.proxy.JsonP',
          buildUrl: function(request) {
              var me = this, url = this.getUrl(request);
              console.log(url);
              request.url = 'http://website.com/Top' + request.params.page + '.json';
              return me.callParent([request]);
          }
      });
  
  });
  </code></pre>
  
  <p>And the content of the json files are:</p>
  
  <p>Top1.json:</p>
  
  <pre><code>Ext.data.JsonP.callback1({"totalCount":"50", "contents":[{"content_id" : 1, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 2, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 3, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 4, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 5, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 6, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 7, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 8, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 9, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"},{"content_id" : 10, "content" : "&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;&lt;div&gt; Hello World 1&lt;/div&gt;&lt;br&gt;"}]});
  </code></pre>
  
  <p>The other json files follow the same format, with unique content ids, and have the right callbacks (callback2, callback3, callback4 and callback5).</p>
  
  <p>Can someone tell me why all 5 jsonp requests get fired straight away, than waiting for me to scroll?</p>
  
  <p>Thanks,
  Prathap</p>