It's going to be removed from Chromium, see https://crbug.com/812523.

/cc @electron/code-owners 
shell/browser/api/electron_api_app.cc
ElectronBrowserClient::Get()->SetUserAgent(user_agent);
}
std::string App::GetUserAgentFallback() {
  return ElectronBrowserClient::Get()->GetUserAgent();
}
void App::SetBrowserClientCanUseCustomSiteInstance(bool should_disable) {
  ElectronBrowserClient::Get()->SetCanUseCustomSiteInstance(should_disable);
}
bool App::CanBrowserClientUseCustomSiteInstance() {
  return ElectronBrowserClient::Get()->CanUseCustomSiteInstance();
}
#if defined(OS_MACOSX)
bool App::MoveToApplicationsFolder(gin_helper::ErrorThrower thrower,
                                   gin::Arguments* args) {
  return ElectronBundleMover::Move(thrower, args);
}
bool App::IsInApplicationsFolder() {
  return ElectronBundleMover::IsCurrentAppInApplicationsFolder();
}
int DockBounce(gin_helper::Arguments* args) {
  int request_id = -1;
  std::string type = "informational";
  args->GetNext(&type);
  if (type == "critical")
    request_id = Browser::Get()->DockBounce(Browser::BounceType::CRITICAL);
  else if (type == "informational")
    request_id = Browser::Get()->DockBounce(Browser::BounceType::INFORMATIONAL);
  return request_id;
}
void DockSetMenu(electron::api::Menu* menu) {