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

/cc @alespergl 
atom/common/api/atom_api_native_image.cc
}
}  
NativeImage::NativeImage(v8::Isolate* isolate, const gfx::Image& image)
    : image_(image) {
  Init(isolate);
  if (image_.HasRepresentation(gfx::Image::kImageRepSkia)) {
    isolate->AdjustAmountOfExternalAllocatedMemory(
      image_.ToImageSkia()->bitmap()->computeSize64());
  }
  MarkHighMemoryUsage();
}
#if defined(OS_WIN)
NativeImage::NativeImage(v8::Isolate* isolate, const base::FilePath& hicon_path)
    : hicon_path_(hicon_path) {
  
  gfx::ImageSkia image_skia;
  ReadImageSkiaFromICO(&image_skia, GetHICON(256));
  image_ = gfx::Image(image_skia);
  Init(isolate);
  if (image_.HasRepresentation(gfx::Image::kImageRepSkia)) {
    isolate->AdjustAmountOfExternalAllocatedMemory(
      image_.ToImageSkia()->bitmap()->computeSize64());
  }
  MarkHighMemoryUsage();
}
#endif
NativeImage::~NativeImage() {