Blender Git Loki

Fix PlayAnim issue with images gradually loading into cache

Instead of only drawing images on first start, load them into cache.

This resolves a logical problem when images don't load fast enough,
where the animation would load some frames each time until all images
loaded into cache.

In practice this could play back with severe frame skipping many times
times before all images were loaded making playback smooth.

Part of a fix for T81751.