This was a follow-up to an earlier change which also delayed image decompressing. In the description of that change the author wrote: "Andrew McCreight wrote a

This was a follow-up to an earlier change which also delayed image decompressing. In the description of that change the author wrote: "Andrew McCreight wrote a comment that I can’t find now, but basically he said that on one of his machines, that page was extremely slow and painful to scroll through before the change, and after the change it was smooth and pleasant." If you have any examples where the linked changes causes performance degradation, you should try reporting it to the developers.