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

/cc @alespergl 
atom/common/api/atom_api_native_image.cc
}
bool NativeImage::IsTemplateImage() {
  return false;
}
#endif
/
mate::Handle<NativeImage> NativeImage::CreateEmpty(v8::Isolate* isolate) {
  return mate::CreateHandle(isolate, new NativeImage(isolate, gfx::Image()));
}
/
mate::Handle<NativeImage> NativeImage::Create(
    v8::Isolate* isolate, const gfx::Image& image) {
  return mate::CreateHandle(isolate, new NativeImage(isolate, image));
}
/
mate::Handle<NativeImage> NativeImage::CreateFromPNG(
    v8::Isolate* isolate, const char* buffer, size_t length) {
  gfx::Image image = gfx::Image::CreateFrom1xPNGBytes(
      reinterpret_cast<const unsigned char*>(buffer), length);
  return Create(isolate, image);
}
/
mate::Handle<NativeImage> NativeImage::CreateFromJPEG(