News Site uses the same image in different sizes to instead of different images

[bgrins]

This was raised in a Gecko bug https://bugzilla.mozilla.org/show_bug.cgi?id=1915251#c1:

So on each iteration the multiple decodes are because the image is used at different sizes, and the decodes are at different sizes. On a real news site each of those images would be a different image, so it wouldn't be multiple decodes. So that doesn't really seem like a problem. Perhaps the test should be altered to make it more realistic?

Then after an iteration the presshell is destroy which discards the decoded copy immediately, and the new iteration we decode again. We could be slightly less aggressive on this discard perhaps. I believe there was a reason why we were this discard was introduced with a large amount getting accumulated in the past. We could maybe just do the discard a little slower to avoid the re-decodes. The decodes are off main thread, so the speed up would be small likely, and the benefit to real sites limited to less usual conditions I think.

The idea is that it would be more realistic to add a unique placeholder images for each placement on the page rather than using a differently-sized resources/newssite/news-next/dist/placeholder_light.jpg for each:

[rniwa]

Yeah, I noticed this as well. It would be more realistic to have a distinct image for each.

[flashdesignory]

oh yeah, that was on my todo list at some point.
Happy to work on this.