Blender Git Loki

Fix/workaround T51070: Cannot scale procedural texture in compositor

The issue is coming from some weird semi-finished canvas feature, which
was remapping coordinate without applying any differential on the sampling
ellipse (in fact, there is no ellipse, sampling think is always a single
pixel).

The whole thing is just weak in the compositor, for now just bring behavior
back to how it was prior to optimization (multithreading) commit.