Efl.Canvas.Vg.Object: Fix backup size

Summary:
Make the size to be backed up and the size to be compared equal.
and minor fix

Test Plan: N/A

Reviewers: Hermet, herb, kimcinoo

Reviewed By: Hermet

Subscribers: cedric, reviewers, committers

Tags: efl

Differential Revision: https://phab.enlightenment.org/D11925