I forgot to look for other calls to image-size. Looking through the
whole emacs code, only image-mode seems to be making calls to
image-size, which can possibly be including slice property.

So Now, I wrote a wrapper over image-size function which calculates size
From slice property if available, or calls image-size if, only image
property is available.

The patch is attached.

Happy Hacking
Shyam K