[WebGPU] Give a ConvertToBackingContext to SurfaceImpl and SwapChainImpl

[litherum]

db1acf9

[WebGPU] Give a ConvertToBackingContext to SurfaceImpl and SwapChainImpl
https://bugs.webkit.org/show_bug.cgi?id=250964
rdar://104522936

Reviewed by Kimmo Kinnunen.

SurfaceImpl and SwapChainImpl don't actually need a ConvertToBackingContext right now, but
most of the other ***Impl classes need one and have one, so I think it's just generally a
good idea to be consistent with the pattern and give one to all the ***Impl classes. In the
future, when we're developing, I don't think we should have to remember which classes have
a ConvertToBackingContext and which don't.

* Source/WebCore/PAL/pal/graphics/WebGPU/Impl/WebGPUSurfaceImpl.cpp:
(PAL::WebGPU::SurfaceImpl::SurfaceImpl):
(PAL::WebGPU::SurfaceImpl::setLabelInternal):
* Source/WebCore/PAL/pal/graphics/WebGPU/Impl/WebGPUSurfaceImpl.h:
* Source/WebCore/PAL/pal/graphics/WebGPU/Impl/WebGPUSwapChainImpl.cpp:
(PAL::WebGPU::SwapChainImpl::SwapChainImpl):
* Source/WebCore/PAL/pal/graphics/WebGPU/Impl/WebGPUSwapChainImpl.h:

Canonical link: https://commits.webkit.org/259235@main

bfb1b1f

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	✅ 🛠 tv	✅ 🧪 mac-wk2
	✅ 🛠 tv-sim	✅ 🧪 mac-AS-debug-wk2
	✅ 🛠 watch	✅ 🧪 mac-wk2-stress
✅ 🛠 🧪 merge	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 8f5d48b)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	⏳ 🛠 ios	⏳ 🛠 mac	✅ 🛠 wpe	⏳ 🛠 🧪 win
✅ 🧪 bindings	⏳ 🛠 ios-sim	❌ 🛠 mac-AS-debug	⏳ 🛠 gtk	⏳ 🛠 wincairo
✅ 🧪 webkitperl	⏳ 🧪 ios-wk2	⏳ 🧪 api-mac	⏳ 🧪 gtk-wk2
	⏳ 🧪 api-ios	⏳ 🧪 mac-wk1	⏳ 🧪 api-gtk
⏳ 🛠 🧪 jsc	⏳ 🛠 tv	⏳ 🧪 mac-wk2
⏳ 🛠 🧪 jsc-arm64	⏳ 🛠 tv-sim	❌ 🧪 mac-AS-debug-wk2
	⏳ 🛠 watch	⏳ 🧪 mac-wk2-stress
	⏳ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash bfb1b1f)

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

[webkit-commit-queue]

Committed 259235@main (db1acf9): https://commits.webkit.org/259235@main

Reviewed commits have been landed. Closing PR #8942 and removing active labels.