title: Flex 4 Center Rendered CheckBox on DataGridColumn
body: <p>I am having an issue trying to center checkboxes without modifying the structure on  DataGridColumn, after the migration from flex 3 to 4 the checkboxes are not appearing centered, is there any trick to center the checkboxes using css?</p>
  
  <pre><code>&lt;mx:DataGridColumn 
      headerRenderer="mx.controls.CheckBox" 
      itemRenderer="mx.controls.CheckBox"                                 
      textAlign="center"
      editable="false" width="50"/&gt;
  </code></pre>
  
  <p>PD: looks like textAlign="center" is just working for text labels now.</p>