delphi TWebBrowser get HTML source after AJAX load

function TBrowser.GetWebBrowserHTML(const WebBrowser: TWebBrowser): string;
var
  LStream: TStringStream;
  Stream : IStream;
  LPersistStreamInit : IPersistStreamInit;
begin
  try
    if not Assigned(WebBrowser.Document) then exit;
    LStream := TStringStream.Create('', TEncoding.UTF8);
    try
      LPersistStreamInit := WebBrowser.Document as IPersistStreamInit;
      Stream := TStreamAdapter.Create(LStream,soReference);
      LPersistStreamInit.Save(Stream,true);
      result := LStream.DataString;
    finally
      LStream.Free();
    end;
  except
  end;
end;