They were disabled during the Chromium 61 upgrade. Fix them and enable.

/cc @alespergl 
atom/common/api/atom_api_native_image.cc
v8::Local<v8::Value> buffer;
  GURL url;
  if (options.Get("buffer", &buffer) && node::Buffer::HasInstance(buffer)) {
    AddImageSkiaRep(
        &image_skia,
        reinterpret_cast<unsigned char*>(node::Buffer::Data(buffer)),
        node::Buffer::Length(buffer),
        width, height, scale_factor);
    skia_rep_added = true;
  } else if (options.Get("dataURL", &url)) {
    std::string mime_type, charset, data;
    if (net::DataURL::Parse(url, &mime_type, &charset, &data)) {
      if (mime_type == "image/png" || mime_type == "image/jpeg") {
        AddImageSkiaRep(
            &image_skia,
            reinterpret_cast<const unsigned char*>(data.c_str()),
            data.size(),
            width, height, scale_factor);
        skia_rep_added = true;
      }
    }
  }
  
  if (skia_rep_added && IsEmpty()) {
    gfx::Image image(image_skia);
    image_.SwapRepresentations(&image);
  }
}
#if !defined(OS_MACOSX)
void NativeImage::SetTemplateImage(bool setAsTemplate) {