IntersectionObserver callback for a visible sentinel node within a container with CSS transform animations is triggered multiple times, but should only be triggered once

[graouts]

a2fe0bd

IntersectionObserver callback for a visible sentinel node within a container with CSS transform animations is triggered multiple times, but should only be triggered once
https://bugs.webkit.org/show_bug.cgi?id=273928
rdar://127804335

Reviewed by Simon Fraser.

Make sure we use RenderLayer::currentTransform() when querying the target's transform to ensure that it accounts
for accelerated animations. Indeed, RenderLayer::transform() will only account for the transform set on the
`RenderStyle` which does *not* update during the course of an accelerated property animation.

* LayoutTests/imported/w3c/web-platform-tests/intersection-observer/transform-animation-expected.txt: Added.
* LayoutTests/imported/w3c/web-platform-tests/intersection-observer/transform-animation.html: Added.
* Source/WebCore/rendering/RenderBox.cpp:
(WebCore::RenderBox::computeVisibleRectsInContainer const):

Canonical link: https://commits.webkit.org/278763@main

3f120e3

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	⏳ 🛠 wpe-skia
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
	✅ 🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 3f120e3)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	⏳ 🛠 wpe-skia
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
	✅ 🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 278763@main (a2fe0bd): https://commits.webkit.org/278763@main

Reviewed commits have been landed. Closing PR #28537 and removing active labels.