Summary:
In iOS 11, [CADisplayLink](https://developer.apple.com/documentation/quartzcore/cadisplaylink)'s frameInterval was deprecated in favor of preferredFramesPerSecond, but these two properties have different underlying assumptions.
- set frameInterval to 2 for 30fps
- set preferredFramesPerSecond to 30 for 30fps. When you use preferredFramesPerSecond, assume frameInterval is 1.
This fix ensures gifs in <Image> component will animate at same speed regardless of framerate.
Reviewed By: shergin
Differential Revision: D21414014
fbshipit-source-id: 40ab23bab1990cf65d2802830b6835f350999537