title: Remove ExtJs 4 default class
body: <p>I'm trying to remove a default class from an element, however the class does not have a single selector.  The class is assigned like this:</p>
  
  <pre><code>.x3-scope .x-form-grow-sizer {
      font:normal 12px tahoma, arial, helvetica, sans-serif;
  }
  </code></pre>
  
  <p>I've tried this:</p>
  
  <pre><code>Ext.get("test1234567").removeClass(".x3-scope .x-form-grow-sizer");
  </code></pre>
  
  <p>But it doesn't work.  Should it?</p>