code: public boolean isIFrameRequest()
      {
          if (_iframeRequest == null)
          {
              _iframeRequest = _facesContext.getExternalContext().getRequestParameterMap().containsKey(PARTIAL_IFRAME);
          }
          return _iframeRequest;
      }
docs: Extension for
  https://issues.apache.org/jira/browse/MYFACES-2841
  internal extension which detects that the submit is an iframe request
  will be changed for the official version which will come in 2.1
  
  @return true if the current request is an iframe based ajax request