/** Activate a plugin.
  *
  * @param string,... $plugin_name
  *
  * @return static
  */
 public function usePlugin($plugin_name)
 {
     foreach (func_get_args() as $name) {
         if (empty($this->_plugins[$name])) {
             $class = Test_Browser_Plugin::sanitizeClassname($name);
             /* @var $Plugin Test_Browser_Plugin */
             $Plugin = new $class($this->getEncapsulatedObject());
             $this->_plugins[$name] = $Plugin;
             $this->injectDynamicMethod($Plugin->getMethodName(), array($Plugin, 'invoke'));
         }
     }
     return $this;
 }
 /** Initialize the plugin.
  *
  * @return void
  */
 public function initialize()
 {
     parent::initialize();
     $this->_content = null;
 }