procedure DoWork (const doc: ICefDomDocument);
var
 q: ICefDomNode;
begin
 q := doc.GetElementById('q');
 if Assigned(q) then q.SetElementAttribute('value', 'Hello, world');
end;

procedure actDomExecute;
var
 q: ICefDomNode;
begin
  crm.Browser.MainFrame.VisitDomProc(DoWork);
end;

TCustomRenderProcessHandler = class(TCefRenderProcessHandlerOwn)
private
 procedure ProcessDOM(const ADocument: ICefDomDocument);
 procedure ProcessNode(ANode: ICefDomNode);
protected
 function OnProcessMessageReceived(const browser: ICefBrowser;
   sourceProcess: TCefProcessId; const message: ICefProcessMessage): Boolean; override;
public
end;

function TCustomRenderProcessHandler.OnProcessMessageReceived(
 const browser: ICefBrowser; sourceProcess: TCefProcessId;
 const message: ICefProcessMessage): Boolean;
begin
 if (message.Name = 'visitdom') then
 begin
   browser.MainFrame.VisitDomProc(ProcessDOM);
   Result := True;
 end
 else
   Result := False;
end;

CefRenderProcessHandler := TCustomRenderProcessHandler.Create;
TCustomRenderProcessHandler(CefRenderProcessHandler).bFinish := False;

procedure TMainForm.Chrome1LoadEnd(Sender: TObject; const ABrowser: ICefBrowser; const AFrame: ICefFrame; AStatus: Integer);
begin
 if (AStatus = 200) and (ABrowser<>nil) and AFrame.IsMain then
   ABrowser.SendProcessMessage(PID_RENDERER, TCefProcessMessageRef.New('visitdom'));
end;

procedure ProcessNode(ANode: ICefDomNode);
var
 Node1: ICefDomNode;
begin
 if Assigned(ANode) then begin
   Node1 := ANode.FirstChild;
   while Assigned(Node1) do begin
     {Do stuff with node}
     ProcessNode(Node1);
     Node1 := Node1.NextSibling;
   end;
 end;
end;

procedure ProcessDOM(const ADocument: ICefDomDocument);
begin
 ProcessNode(ADocument.Body);
end;

procedure TMainForm.Chrome1LoadEnd(Sender: TObject; const ABrowser: ICefBrowser; const AFrame: ICefFrame; AStatus: Integer);
begin
 if Assigned(AFrame) then AFrame.VisitDomProc(ProcessDOM);
end;