visibility:hidden causes delay before rendering

[kinglozzer]

Describe the bug
When using the following CSS:

img.lazyload:not([src]) {
    visibility: hidden;
}

There is a noticeable delay before the image gets loaded. I’m not sure why - Chrome’s JS profiler suggests it’s not actually doing anything at all (“idle frame” for a second or so before it attempts loading). It also happens in Safari and Firefox (MacOS 10.14.5 here). It doesn’t happen when using opacity:

img.lazyload:not([src]) {
   opacity: 0.001;
}

To Reproduce
https://jsbin.com/zecodopaqo/edit?html,css,output

[aFarkas]

Thank you. That was quite a bug!!!