* Electron Version 6.0.0-beta.12
* Operating System Windows 10 64 bit

Expected Behavior
webContents.print() should send print a job to the specified printer

Actual behavior
Nothing happens. Callback gets called much latter, for example on program exit.

To Reproduce
let print_options = { 
    silent: true,
    printBackground: true,
    deviceName: barcode_device_name 
}
print_window.webContents.print(print_options, (data) => {
    console.log(`print result: ${data}`)
})

Related to #17260
shell/browser/api/atom_api_web_contents.cc
v8::Local<v8::Value> val,
                     printing::DuplexMode* out) {
    std::string mode;
    if (ConvertFromV8(isolate, val, &mode)) {
      if (mode == "simplex") {
        *out = printing::SIMPLEX;
        return true;
      }
      if (mode == "longEdge") {
        *out = printing::LONG_EDGE;
        return true;
      }
      if (mode == "shortEdge") {
        *out = printing::SHORT_EDGE;
        return true;
      }
    }
    return false;
  }
};
#endif
template <>
struct Converter<WindowOpenDisposition> {
  static v8::Local<v8::Value> ToV8(v8::Isolate* isolate,