This small plugin enables WordPress to properly resize animated GIFs. On many installations, WordPress will resize animated GIFs by taking the first frame only. This plugin fixes this problem.
Note that this plugin can only resize animated GIFs at the moment. I will work on supporting rotations, reflections, etc when I have enough time.
It is exactly what I looked for! Works like a charm!
Thank you so much!
I just tested this on WordPress 4.4.1 and it caused an error that blocked gif uploads all together.