* 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
v8::Isolate* isolate, const GURL& url) {
  std::string mime_type, charset, data;
  if (net::DataURL::Parse(url, &mime_type, &charset, &data)) {
    if (mime_type == "image/png")
      return CreateFromPNG(isolate, data.c_str(), data.size());
    else if (mime_type == "image/jpeg")
      return CreateFromJPEG(isolate, data.c_str(), data.size());
  }
  return CreateEmpty(isolate);
}
/
void NativeImage::BuildPrototype(