if frame.IsMain then

Chromium1.Browser.MainFrame.ExecuteJavaScript(MemoJS.Text, Chromium1.Browser.MainFrame.Url, 0);

var
  FrameCount: NativeUInt;
  CefFrameIdentifierArray: TCefFrameIdentifierArray;
begin
...
...
  browser.GetFrameIdentifiers(FrameCount, CefFrameIdentifierArray);
  
  CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'browser.FrameCount: ' + FrameCount.ToString);
  CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'CefFrameIdentifierArray: ' + Length(CefFrameIdentifierArray).ToString);

browser.FrameCount

procedure TMiniBrowserFrm.Chromium1LoadEnd(Sender: TObject;
  const browser: ICefBrowser; const frame: ICefFrame;
  httpStatusCode: Integer);
var
  TempMsg: ICefProcessMessage;
begin

  if frame.IsMain then
  begin
    Memo1.Lines.Add('main frame load end: ' + TimeToStr(now));
    Chromium1.Browser.MainFrame.ExecuteJavaScript(MemoJS.Text, Chromium1.Browser.MainFrame.Url, 0);

    // Use the ArgumentList property if you need to pass some parameters.
    TempMsg := TCefProcessMessageRef.New(MSG3);// в MSG3 какой-то текст, в которому будем ловить сообщение в процедуре GlobalCEFApp_OnProcessMessageReceived()
    frame.SendProcessMessage(PID_RENDERER, TempMsg);// сообщение для процесса рендеринга
  end;
end;

procedure GlobalCEFApp_OnProcessMessageReceived(const browser       : ICefBrowser;
                                                const frame         : ICefFrame;
                                                      sourceProcess : TCefProcessId;
                                                const message       : ICefProcessMessage;
                                                var   aHandled      : boolean);
VAR
  TempVisitor : TCefFastDomVisitor2;
begin
  aHandled := False;
  CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'GlobalCEFApp_OnProcessMessageReceived');
  if browser <> nil then
  begin
    CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'message.name = ' + message.name);

    if message.name = MSG3 then
    begin
      TempVisitor := TCefFastDomVisitor2.Create(browser, Frame, DOMVisitor_OnDocAvailableSearch);
      frame.VisitDom(TempVisitor);
    end;
  end;

  aHandled := True;
end;

procedure DOMVisitor_OnDocAvailableSearch(const browser: ICefBrowser; const frame: ICefFrame; const document: ICefDomDocument);
begin
  CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'DOMVisitor_OnDocAvailableSearch');
  SimpleDOMIteration(document, frame);// frame передаем для того, чтобы отправить сообщение обратно в TChromium
end;

procedure SimpleDOMIteration(const aDocument: ICefDomDocument; const frame: ICefFrame);
var
  TempHead, TempChild : ICefDomNode;
  msg: ICefProcessMessage;
begin
  CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'SimpleDOMIteration');

  try
    if aDocument <> nil then
    begin
        TempHead := aDocument.Body;

        if TempHead <> nil then
        begin
          TempChild := TempHead.FirstChild;

          while TempChild <> nil do
          begin
            CefLog('CEF4Delphi', 1, CEF_LOG_SEVERITY_INFO, 'Head child element : ' + TempChild.Name + ', ElementInnerText: ' + Trim(TempChild.ElementInnerText));
// отправляем сообщение обратно в TChromium
            Msg := TCefProcessMessageRef.New(msg2);
            msg.ArgumentList.SetString(0, 'TempChild.ElementInnerText: ' + Trim(TempChild.ElementInnerText));
            frame.SendProcessMessage(PID_BROWSER, msg);

            TempChild := TempChild.NextSibling;
          end;
        end;
    end;
  except
    on e : exception do
      if CustomExceptionHandler('SimpleDOMIteration', e) then raise;
  end;
end;

procedure TMiniBrowserFrm.Chromium1ProcessMessageReceived(Sender: TObject;
  const browser: ICefBrowser; const frame: ICefFrame;
  sourceProcess: TCefProcessId; const message: ICefProcessMessage;
  out Result: Boolean);
begin
  Memo1.Lines.Add('Chromium1ProcessMessageReceived-1');

  Result := False;
  if (message = nil) or (message.ArgumentList = nil) then exit;

  Memo1.Lines.Add(message.Name);

  if message.Name = MSG2 then
  begin
    Memo1.Lines.Add(MSG2);
    Memo1.Lines.Add(message.ArgumentList.GetString(0));// данные здесь
  end;

  Result := True;
end;

frame.VisitDom(TempVisitor);