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

/cc @electron/code-owners 
shell/browser/api/electron_api_app.cc
if (command_line->HasSwitch(service_manager::switches::kNoSandbox)) {
    const base::CommandLine::CharType* noSandboxArg =
        FILE_PATH_LITERAL("--no-sandbox");
    base::CommandLine::StringVector modified_command_line;
    for (auto& arg : command_line->argv()) {
      if (arg.compare(noSandboxArg) != 0) {
        modified_command_line.push_back(arg);
      }
    }
    command_line->InitFromArgv(modified_command_line);
  }
}
void App::EnableSandbox(gin_helper::ErrorThrower thrower) {
  if (Browser::Get()->is_ready()) {
    thrower.ThrowError(
        "app.enableSandbox() can only be called "
        "before app is ready");
    return;
  }
  auto* command_line = base::CommandLine::ForCurrentProcess();
  RemoveNoSandboxSwitch(command_line);
  command_line->AppendSwitch(switches::kEnableSandbox);
}
void App::SetUserAgentFallback(const std::string& user_agent) {