How to execute javascript commands via TChromium?

I'm trying to execute javascript code in TChromium , but I get an error:

Memory could not be read.

 procedure TForm1.Button2Click(Sender: TObject); var js: string; begin js := 'document.execCommand(''SaveAs'')'; chromium1.Browser.MainFrame.ExecuteJavaScript(js, 'http://www.google.ru/', 0); end;