* Electron version: latest
* Operating system: MacOS

The TouchBar API (and MacOS in general) let's you pass an `imageNamed` param to NSImage to get the default OS image. For example: `[NSImage imageNamed:@"NSTouchBarGoUpTemplate"];` creates an NSImage with the default up chevron icon on MacOS. 

It would be pretty neat-o to allow TouchBar users to do something like this: 

```javascript
new TouchBarButton({
  icon: nativeImage.createFromMacOSNamedImage('NSTouchBarGoUpTemplate')
})
```

...and maybe that would just no-op with `nativeImage.createEmpty()` on non-MacOS platforms. 

I guess this is really bigger than just TouchBar because this API could benefit `Menu` for example as well, or anywhere else where you use `nativeImage`. 


atom/common/api/atom_api_native_image.cc
float scale_factor = GetScaleFactorFromOptions(args);
  const SkBitmap bitmap =
      image_.AsImageSkia().GetRepresentation(scale_factor).sk_bitmap();
  SkPixelRef* ref = bitmap.pixelRef();
  if (!ref)
    return node::Buffer::New(args->isolate(), 0).ToLocalChecked();
  return node::Buffer::Copy(args->isolate(),
                            reinterpret_cast<const char*>(ref->pixels()),
                            bitmap.getSafeSize()).ToLocalChecked();
}
v8::Local<v8::Value> NativeImage::ToJPEG(v8::Isolate* isolate, int quality) {
  std::vector<unsigned char> output;
  gfx::JPEG1xEncodedDataFromImage(image_, quality, &output);
  if (output.empty())
    return node::Buffer::New(isolate, 0).ToLocalChecked();
  return node::Buffer::Copy(
      isolate,
      reinterpret_cast<const char*>(&output.front()),
      output.size()).ToLocalChecked();
}
std::string NativeImage::ToDataURL(mate::Arguments* args) {