* Electron version: 1.4.4
* Operating system: win10

Hi,
Example described [here](https://github.com/electron/electron/blob/master/docs/api/global-shortcut.md) works with v1.4.0 but doesn't seem to work with v1.4.4 or v1.4.5.  Method `globalShortcut.isRegistered ` returns true, but the callback isn't called. 

Thanks!
atom/browser/api/atom_api_system_preferences.cc
}
#if !defined(OS_MACOSX)
bool SystemPreferences::IsDarkMode() {
  return false;
}
#endif
bool SystemPreferences::IsInvertedColorScheme() {
  return color_utils::IsInvertedColorScheme();
}
mate::Handle<SystemPreferences> SystemPreferences::Create(
    v8::Isolate* isolate) {
  return mate::CreateHandle(isolate, new SystemPreferences(isolate));
}
void SystemPreferences::BuildPrototype(
    v8::Isolate* isolate, v8::Local<v8::FunctionTemplate> prototype) {
  prototype->SetClassName(mate::StringToV8(isolate, "SystemPreferences"));
  mate::ObjectTemplateBuilder(isolate, prototype->PrototypeTemplate())
#if defined(OS_WIN)
      .SetMethod("getAccentColor", &SystemPreferences::GetAccentColor)
      .SetMethod("isAeroGlassEnabled", &SystemPreferences::IsAeroGlassEnabled)
      .SetMethod("getColor", &SystemPreferences::GetColor)
#elif defined(OS_MACOSX)
      .SetMethod("postNotification",
                 &SystemPreferences::PostNotification)
      .SetMethod("postLocalNotification",
                 &SystemPreferences::PostLocalNotification)
      .SetMethod("subscribeNotification",
                 &SystemPreferences::SubscribeNotification)