* 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
const gfx::Rect& rect) {
  gfx::ImageSkia cropped = gfx::ImageSkiaOperations::ExtractSubset(
      image_.AsImageSkia(), rect);
  return mate::CreateHandle(isolate,
                            new NativeImage(isolate, gfx::Image(cropped)));
}
void NativeImage::AddRepresentation(const mate::Dictionary& options) {
  int width = 0;
  int height = 0;
  float scale_factor = 1.0f;
  options.Get("width", &width);
  options.Get("height", &height);
  options.Get("scaleFactor", &scale_factor);
  bool skia_rep_added = false;
  gfx::ImageSkia image_skia = image_.AsImageSkia();