Fix for broken Grid scrollers in Extjs 4.0.2a

gistfile1.js

Ext.require('Ext.grid.Panel',function(){
  Ext.override(Ext.grid.Panel, {
	constructor: function() {
        this.on('scrollershow', function(scroller) {
          if (scroller && scroller.scrollEl) {
            scroller.clearManagedListeners(); 
            scroller.mon(scroller.scrollEl, 'scroll', scroller.onElScroll, scroller); 
          }
        });
		this.callOverridden();
	}
  });
});