Set cef srcoll bar's css style

void ClientHandler::OnLoadStart(CefRefPtr browser,
                                CefRefPtr frame) {
  REQUIRE_UI_THREAD();
  std::string js = "var headID = document.head;"
                   "var styleNode = document.createElement('style');"
                   "styleNode.type='text/css';"
                   "styleNode.appendChild(document.createTextNode('::-webkit-scrollbar {width:17px; } ::-webkit-scrollbar-thumb { background: rgba(255,0,0,0.8); }'));"
                   "document.head.appendChild(styleNode);";
  frame->ExecuteJavaScript(js, frame->GetURL(), 0);
                   //"styleNode.appendChild(document.createTextNode('::-webkit-scrollbar {width:38px; height:38px;} ::-webkit-scrollbar-track {-webkit-box-shadow:inset 0 0 6px rgba(0,0,0,0.3); } ::-webkit-scrollbar-thumb { border-radius: 10px; -webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5); }'));"
}