code: function(className, testFn, scope) {
          var me = this,
              dom = me.dom,
              hasTest = Ext.isFunction(testFn);
              
          me.on("mousedown", function() {
              if (hasTest && testFn.call(scope || me, me) === false) {
                  return false;
              }
              Ext.fly(dom, INTERNAL).addCls(className);
              var d = Ext.getDoc(),
                  fn = function() {
                      Ext.fly(dom, INTERNAL).removeCls(className);
                      d.removeListener("mouseup", fn);
                  };
              d.on("mouseup", fn);
          });
          return me;
      }
docs: Sets up event handlers to add and remove a css class when the mouse is down and then up on this element (a click effect)
  @param {String} className The class to add
  @param {Function} [testFn] A test function to execute before adding the class. The passed parameter
  will be the Element instance. If this functions returns false, the class will not be added.
  @param {Object} [scope] The scope to execute the testFn in.
  @return {Ext.dom.Element} this