Separated layers should support border-radius

[etiennesegonzac]

d634b45

Separated layers should support `border-radius`
https://bugs.webkit.org/show_bug.cgi?id=282834
<rdar://137275518>

Reviewed by Simon Fraser.

When using separated layers, we need to apply the corner radius to the
main layer if at all possible in order to get the expected visual effect.
Introduce a new clipping strategy for these layers.

* Source/WebCore/rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::updateConfiguration):
Enable composited descendant clipping on separated layers.
(WebCore::RenderLayerBacking::updateContentsRects):
Generate a content clipping rect for all separated layers.

* Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp:
(WebCore::GraphicsLayerCA::updateClippingStrategy):
Set the corner radius on the main layer for separated layers. We also
relax the application to even corners (as opposed to uniform) since
masking won't yield the expected effect.

* Source/WebCore/rendering/RenderLayerCompositor.h:
* Source/WebCore/rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::isSeparated):
Add a helper method to test if a RenderObject requires a separated
layer.

* LayoutTests/platform/visionos/transforms/separated-expected.txt:
* LayoutTests/platform/visionos/transforms/separated.html:
Update the test to cover this by adding a `border-radius` to the
transformed elements.

Canonical link: https://commits.webkit.org/286384@main

ef9be1c

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	⏳ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	⏳ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	✅ 🧪 win-tests
✅ 🧪 webkitperl	⏳ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	⏳ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	⏳ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🧪 vision-wk2	🧪 mac-intel-wk2
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash ef9be1c)

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	⏳ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	⏳ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	✅ 🧪 win-tests
✅ 🧪 webkitperl	⏳ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	⏳ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	⏳ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🧪 vision-wk2	🧪 mac-intel-wk2
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 286384@main (d634b45): https://commits.webkit.org/286384@main

Reviewed commits have been landed. Closing PR #36397 and removing active labels.